The Communal Dimension of the Mitzva of Lulav
Translated by David Silverberg
The gemara (Sukka 41b) understands the word, "u-lekachtem" (you shall take), which appears in the Torah in reference to the mitzva of lulav, as requiring each individual to perform this mitzva. One person cannot fulfill the obligation on behalf of others. The Rash Mi-Shantz, in his commentary to the Torat Kohanim, raises the following question:
"Why must we derive [from a verse] that one cannot fulfill the obligation of behalf of others? There are many mitzvot, such as tefillin, tzitzit, and sukka, that are required of each individual. It does not at all stand to reason that one can fulfill an obligation on behalf of others, except regarding [mitzvot that require] listening, such as blowing the shofar!"
The Meiri answers that in the absence of a textual source to the contrary, one might have understood the mitzva of lulav not as an individual obligation, but rather as a responsibility of the Beit Din (the Jewish court). This approach receives support from a parallel halakhic extrapolation from a verse regarding sefirat ha-omer: "'You shall count for yourselves' - that each individual should conduct his own counting" (Menachot 65b). Indeed, Tosafot (Sukka 29b) draw a comparison between this derivation and that regarding lulav. Clearly, the derivation concerning sefirat ha-omer comes to dispel the notion that counting the omer resembles the obligation of counting the years of shemitta and yovel, which is incumbent only upon the Beit Din.
According to this approach, the gemara considered the possibility of viewing the mitzva of lulav as a communal - rather than personal - obligation. Although the Gemara concludes that the obligation applies to each individual, this does not necessarily imply that no communal obligation exists beyond the personal requirement. Can we prove that this mitzva does, in fact, feature a communal element? On what halakhic concepts might we base such an obligation?
- THE RELATIONSHIP BETWEEN LULAV IN THE MIKDASH AND OUTSIDE THE MIKDASH
The first place to look for a communal element would be the mitzva of lulav as observed in the Mikdash (Temple). As the "mountain to which all mouths turn," the Beit Ha-mikdash marks the focal point of many communal mitzvot, such as public sacrifices (korbenot tzibbur), the holiday pilgrimages and Hakhel (the septennial nationwide assembly in Yerushalayim). We likewise find that the group of people gathered in the azara (courtyard outside the Mikdash) attain the formal status of a "tzibbur," representatives of the nation at large. It stands to reason, then, that the mitzva of lulav in the Mikdash, derived from the verse, "and you shall rejoice before the Lord your God," constitutes a communal obligation.
Proof to this effect may be drawn from the encircling of the altar with the lulav described in the mishna (45a), in which large crowds of people participated. The Or Zarua (315) describes it as follows, based on the Yerushalmi:
"All of Yisrael, old and young, would take their lulavim in their right hands and their etrogim in their left hands and encircle [the altar]."
If we are correct, then the communal nature of the mitzva in the Mikdash may impact upon the nature of the requirement elsewhere. We will demonstrate this impact by clarifying the relationship between the mitzva of lulav in the Mikdash and that outside the Temple grounds.
As we know, the obligation of lulav applies on the level of Torah law for only one day outside the Mikdash; according to the Torah, the seven-day requirement pertains only in the Temple. As mentioned, this distinction is derived from the verse, "...and you shall rejoice before the Lord your God [i.e. in the Temple] for seven days." How must we understand the difference between these two obligations, in the Mikdash and elsewhere? Do we have two distinct mitzvot, or a single mitzva whose time-frame changes depending on location?
Rav Soloveitchik z"l is cited ("Reshimot Shiurim," p.115) as associating this question with a dispute among the Rishonim concerning the various disqualifications of the four species. Without going into detail, let us just cite a ruling of the Rambam:
"All these disqualifications - whether due to physical defects or because of their having been stolen - apply only on the first day of Yom Tov. But on the second day of Yom Tov, as well as the other days, everything is valid. However, if a disqualification results from idolatry or because a given etrog is forbidden for consumption, it is invalid both on the first day of Yom Tov and the other days." (Hilkhot Lulav 8:9)
Rav Soloveitchik observed that the Rambam here draws no distinction between the Mikdash and other locations. In all places, it seems, physical defects do not disqualify the four species after the first day of Sukkot. The Rav deduced that according to the Rambam, the seven-day obligation in the Mikdash constitutes an independent mitzva, separate and apart from the one-day requirement in other areas. For this reason, the standards required for the lulav and etrog throughout the seven days in the Mikdash do not correspond to those needed on the first day in other locations.
This conclusion, however, becomes very difficult in light of the Rambam's comments in his "koteret" (introductory remarks) to Hilkhot Lulav, where he succinctly defines the mitzva of lulav: "To take the lulav in the Mikdash for all seven days of Chag [Sukkot]." In his Sefer Ha-mitzvot (mitzvat asei 169), too, the Rambam offers only a single definition of this mitzva:
"He has commanded us to take the lulav and rejoice with it before God for seven days… The laws of this mitzva have already been explained in the third chapter of [Massekhet] Sukka, and there it is explained that the obligation of this mitzva extends for seven days only in the Mikdash, whereas in other places people are biblically obligated only on the first day."
Clearly, the Rambam recognizes only a single mitzva. He also introduces the novel theory that this single mitzva does not comprise one general mitzva that applies everywhere, only with different time-frames in different areas. Instead, this mitzva is defined primarily as taking the lulav in the Mikdash, and the framework of the mitzva in the Mikdash somehow includes the obligation outside the Mikdash, as well. This appears to contradict the Rambam's own position, that with regard to disqualifying a lulav we do not compare the one-day obligation outside the Mikdash and the seven-day mitzva in the Temple.
- TAKING THE LULAV ON SHABBAT
Perhaps we can better understand the Rambam's view by considering his comments regarding the applicability of this mitzva on Shabbat (Hilkhot Lulav 7:13-17):
"If Shabbat falls after the first day of Sukkot, [the lulav] is not taken on Shabbat, because of a decree [issued out of concern that] someone may perhaps bring it in his hand four cubits in a public domain [in violation of Shabbat], just as [Chazal] decreed regarding [the mitzva of] shofar.
Why did they not issue such a decree on the first of Yom Tov as well? Because [on the first day] lulav constitutes a Torah obligation even outside the Mikdash. It thus turns out that the status of the first day and that of the other days are not equivalent, as on the other days of Sukkot one is not obligated [by Torah law] to take [the lulav], except in the Mikdash…
When the Beit Ha-mikdash stood, the lulav was taken on the first day that fell on Shabbat, [both in the Mikdash] as well as in other places in Eretz Yisrael that knew with certainty that this day was the first day of Sukkot. But in the distant areas, where they did not know when Rosh Chodesh was declared, they would not take the lulav out of doubt.
But when the Beit Ha-mikdash was destroyed, the Sages forbade taking the lulav on Shabbat on the first day, even for residents of Eretz Yisrael who declared the newmonth, because of the residents of other places who did not know when the new month was declared. [They decreed this] in order that everyone be the same in this regard and so that there would not arise a situation where one group was taking on Shabbat while the others would not, since the obligation of the first day is the same everywhere and there was no longer a Mikdash upon which to depend."
The Rambam here lists three stages in which the taking of the lulav on Shabbat was gradually minimized (and ultimately eliminated altogether). First, Chazal left the obligation in place only on the first day, when the Torah obligation applies everywhere. In the next phase, they allowed the performance of this mitzva on Shabbat only in those areas where the people knew when Rosh Chodesh was declared. Finally, with the destruction of the Temple, they prohibited it on Shabbat entirely, in order to avoid divergent practices in different areas.
A look at the beginning of the fourth chapter of Masekhet Sukka reveals that the Rambam here adds nothing of his own except his final words: "and there was no longer a Mikdash upon which to depend." What does he mean? Clearly, the Rambam had difficulty understanding the need to avoid divergent practices. If Chazal felt it necessary to ensure a single practice in all areas, why did they issue this decree only after the Temple's destruction? If the Torah obligation warranted taking the lulav on the first day even on Shabbat before the destruction, then why should the concern for uniformity suddenly override this obligation after the destruction?
The Rambam answers that when "there is a Mikdash upon which to depend" we disregard the concern for uniform practices. But this answer seems inexplicable and untenable. It is inexplicable because this explanation works only to justify taking the lulav in the Mikdash. Why does the presence of the Mikdash warrant that all residents of Eretz Yisrael, who live away from the Mikdash but know when Rosh Chodesh was declared, take the lulav on the first day that falls on Shabbat? Additionally, this explanation seems entirely implausible. The Rambam himself (earlier in the citation) stressed - based on the gemara - that it is the obligation in all locations which overrides Shabbat. If the Mikdash were the criterion that warrants taking the lulav on Shabbat, then the mitzva should be performed in the Mikdash on Shabbat even if Shabbat falls on one of the last six days of the holiday! How can one claim that we cannot override Shabbat without a Mikdash, if the mitzva in the Mikdash itself does not override Shabbat?
C. TWO LEVELS OF OBLIGATION IN THE MIKDASH
It seems that the Rambam viewed the obligation of lulav in the Mikdash as a communal obligation; such a perspective allows for the definition of the mitzva in other locations as an extension of that in the Mikdash. The public performance of this mitzva occurs in the Temple, the site of the nation's emissaries and representatives. Thereafter, the communal mitzva in the Temple brings together all those taking the lulav in other locations, who join the communal performance centered in Jerusalem. The Rambam therefore counts only one mitzva: to take the lulav in the Mikdash.
On the first day of Sukkot, this general framework contains an additional detail, "u-lekachtem," requiring the personal performance of every individual. Even this personal obligation, however, is intended to join the general performance of this mitzva, to contribute to it and take part in it. Although the disqualification due to physical defects applies only to the individual performance, this detail does not undermine the additional function assigned to this act: to be woven into the general framework of the collective performance.
We may speculate that the Rambam arrived at this understanding from the gemara's explanation as to why the mitzva of lulav overrides Shabbat only on the first day of Sukkot. As we saw, the gemara attributed this to the universal obligation that applies specifically on the first day. Such an assertion appears to contradict all our basic assumptions. In all other contexts, it is understood that only the Temple service - and specifically the communal service, more so than individual offerings  - overrides Shabbat. For good reason, the Yerushalmi (3:11) writes that logically, only in the Mikdash should the taking of the lulav have overridden Shabbat; however, a textual derivation from a verse calls for overriding Shabbat in other locations as well. The Bavli, however, does not invoke any textual basis for this halakha. It seems to have intuited the ability of obligation on the first day to override Shabbat.
The obvious difficulty arises: how can the Bavli ignore the mitzva of the Mikdash and attribute the power to override Shabbat to an obligation applicable outside the Temple, an individual requirement unrelated to the community at large? Clearly, Chazal drew no distinction between the mitzva in the Mikdash and that observed elsewhere. No such distinction can be sustained because taking the lulav both in and outside the Mikdash comprise a single mitzva; the obligation in other places constitutes but an extension of the communal observance in the Mikdash.
Chazal distinguished between the first day and the rest because the Torah required that the communal observance on the first day take on a special quality, that it extend beyond the confines of the Temple into every home, where it demands the identification and participation of each individual. According to this, the singularity of the first day is expressed not only outside the Mikdash, but even within the mitzva related to the Mikdash. The distinction thus involves two levels within the same mitzva, rather than two separate mitzvot.
A careful reading of our citation from the Rambam yields this understanding, which in fact emerges explicitly from the Rambam's Commentary on the Mishna (Sukka, beginning of chapter 4):
"We do not issue this decree [to refrain from taking the lulav on Shabbat] on the first day of Yom Tov, since this obligation is more stringent, as it is obligatory even outside the Temple, as we explained."
With this understanding in mind, we can understand the Rambam's comments concerning the taking of the lulav on Shabbat. As we have seen, a distinction exists even outside the Mikdash between the periods before and after the Temple's destruction. True, the taking of the lulav outside the Mikdash may assume a communal quality even without a Temple, by virtue of the entire nation's participation. Nevertheless, the heart of this communal quality is absent without a Mikdash. We therefore cannot allow lulav to override Shabbat nowadays. This is what the Rambam means when he writes that nowadays lulav does not override Shabbat because "there is no Temple upon which to depend."
One problem, however, remains unresolved. If the obligation outside the Mikdash overrides Shabbat only because it extends the observance in the Temple, then it is self-evident that it cannot override Shabbat nowadays. The Rambam, however, elaborates at great length in his explanation, emphasizing the weight of the uniformity consideration. Why must the Rambam resort to this issue? True, he had little choice in the matter, as the gemara had already introduced this factor: "Since we [in Bavel] do not override [Shabbat], they [in Eretz Yisrael] likewise do not override [Shabbat]" (43b). The Rambam's question thus arises regarding the gemara: if we afford such importance to the uniformity consideration, then lulav should not have overridden Shabbat even during the times of the Temple. We must therefore accept the Rambam's explanation that only the Mikdash-related mitzva can override Shabbat. But if so, why do both the gemara and the Rambam suggest that if not for the interest in uniformity we would override Shabbat even nowadays?
We may raise a similar question from the Gemara in 43a. The Gemara there posits that lulav overrides Shabbat on the first day because the obligation applies outside the Mikdash on the level of Torah law. According to what we have seen, this means that the obligation in the Mikdash receives added vigor on the first day of Sukkot through its extension to other areas. Chazal therefore saw fit to allow for the overriding of Shabbat only on the first day. However, the gemara then immediately asks, if this is so, why does lulav not override Shabbat on the first day in the post-Temple era as well? In light of our explanation of the Rambam, this question has no basis. As we saw, without the Temple, the primary communal fulfillment of the obligation cannot be achieved. Why, then, did the gemara fail to recognize a distinction between the Temple and post-Temple eras? Granted, one could have argued the case to allow lulav to override Shabbat even without a Temple, if we view the nationwide performance of this mitzva as a communal observance capable of overriding Shabbat even nowadays. But how could the gemara assume that this should be so, based solely upon the situation before the destruction? In order to resolve these difficulties, we must examine the change that occurred regarding the mitzva of lulav after the Temple's destruction.
- THE ENACTMENT OF RABBAN YOCHANAN BEN ZAKAI
After the destruction, Rabban Yochanan Ben Zakai instituted that we take the lulav all seven days of Sukkot to commemorate the observance in the Temple (41a). Why did he not issue similar legislation concerning the mitzva of arava? The gemara explains that unlike the mitzva of arava, the mitzva of lulav has associated with it a Biblical obligation outside the Mikdash. The Ritva and Ran explain that since a Biblical requirement exists outside the Mikdash on the first day, only a seven-day observance can serve as a discernible commemoration of the Temple observance. The practice of taking the arava, by contrast, has no Biblical source outside the Temple. Therefore, taking the arava for even a single day effectively commemorates the original practice in the Mikdash.
We may, however, suggest a different interpretation, one that better accommodates the straightforward reading of the gemara. Given the Biblical obligation associated with taking the lulav outside the Mikdash, extending the obligation to the other days is a reasonable expansion onto the Torah law. A seven-day requirement outside the Temple thus qualifies as "ke-ein de-orayta," closely enough related to Torah law to justify the rabbinic enactment. Taking the arava, by contrast, has no precedent outside the Temple on the level of Torah law, and may therefore not be introduced as a seven-day requirement to commemorate the Mikdash. As in all rabbinic enactment, Chazal tried as much as possible to model their legislation after Torah law (see Gittin 65a).
Indeed, Rashi, in his commentary on this gemara, seems to adopt this approach: "One day, however, has [Biblical] roots; arava, by contrast, has no Biblical roots outside the Temple." Despite the simplicity of this reading of the gemara, the Ritva and Ran refused to accept this understanding. Although they do not explain why, the reason seems clear. Rashi's reading suffers from a basic logical flaw: taking the lulav in commemoration of the Temple cannot possibly follow the Biblical model of taking the lulav outside the Temple. At best, the seven-day commemoration can extend the obligation outside the Temple on the first day. It bears no connection, however, to the obligation in the Temple of "you shall rejoice before God," and thus cannot commemorate the observance in the Temple.
This problem exists only if we view the mitzva outside the Temple as separate and apart from that in the Mikdash. Naturally, then, according to the Rambam's view we may accept Rashi's straightforward reading of the gemara. By its very nature, the mitzva of lulav in the Mikdash constitutes a communal obligation. Thus, Rabban Yochanan Ben Zakai did not merely require a commemoration, but rather introduced a new channel of the communal obligation, requiring the participation of the entire nation, rather than just its representatives in the Temple.
The gemara explains that Rabban Yochanan based his legislation on the one-day Biblical obligation outside the Mikdash, but not because this obligation stands independent of that in Mikdash. To the contrary, this mitzva proves that those outside the Mikdash take part in the mitzva of the Temple; transferring the mitzva to them entirely after the destruction thus does not involve an unreasonable extension of the Torah obligation. Regarding arava, by contrast, the Torah does not recognize any obligation outside the Mikdash.
In summary, the fact that the gemara views Rabban Yochanan's enactment as built upon a model of Torah obligation shows that his legislation involves more than a simple commemoration. It relies on the communities outside the Temple as a substitute for the Temple. This daring step is possible only with regard to lulav, where even on the level of Torah law the nation at large takes part in the mitzva of the Mikdash. No such claim can be made regarding arava.
We can now understand why the gemara initially assumed that overriding Shabbat when the Temple stood should dictate doing so after the destruction as well. Nowadays, the communities outside the Mikdash replace the Mikdash with regard to this mitzva; for this reason we take the lulav all seven days. This substitution should therefore be reflected on the first day of Sukkot as well. With Rabban Yochanan's enactment, the performance on the first day transformed from an observance of individuals to a communal observance. The first day has now taken on the communal quality that was previously focused upon the Mikdash. Assuming that Chazal loyally followed the model of Torah law when introducing their legislation, lulav should override Shabbat on the first day even after the Temple's destruction.
Of course, the gemara concludes that this is not the case. This conclusion likely results from a decision not to abide so strictly by the "ke-ein de-orayta" principle, and to allow for some discrepancy between taking the lulav nowadays and in the Temple. After all, the communal observance nowadays is but a substitute for that in the Mikdash; this substitution does not warrant overriding Shabbat or giving rise to divergent practices. The debate in this gemara revolves around the extent to which the performance outside the Mikdash nowadays must parallel the original observance in the Temple. The Rambam naturally rules in accordance with the Gemara's conclusion: we must not insist on a perfect correspondence if this will result in divergent practices.
- ADDITIONAL RAMIFICATIONS OF THE COMMUNAL ELEMENT OF LULAV
It is worth noting the relationship between this approach and two other points that emerge from the gemara's discussion towards the beginning of the fourth chapter.
The gemara (42b) explains that we do not take the lulav on Shabbat out of concern lest someone carry it through a public domain (in violation of the strictures of Shabbat). Yet the lulav was taken on the first day of Sukkot even when it fell on Shabbat, since on the first day a Biblical requirement exists even outside the Mikdash. This sugya appears to contradict its own application of this concern to the mitzva of shofar, explaining that we do not blow shofar on Shabbat in order to avoid Shabbat violation. Now, the requirement of shofar applies as a Torah obligation in all locations; why does it not override this concern?
The Rishonim raised several resolutions to this problem. Tosafot write that a greater concern arises regarding shofar, which requires skill and expertise, potentially prompting one to take it to an expert to learn how to blow. The Ba'al Ha-ma'or holds that shofar does not override Shabbat since many of the sounds blown are required only by rabbinic enactment. The Ramban answers that places outside the area of the Mikdash could not know on which day the High Court declared Rosh Hashana. Chazal therefore did not allow shofar blowing on Shabbat, in light of the question as to whether that day was in fact Rosh Hasha.
Based on our understanding of the Rambam, however, this question never even arises. Let us take a careful look at the gemara's wording:
"[On] the first day, which has [an obligation] from the Torah outside the Mikdash, the rabbis did not decree [that we refrain from taking the lulav]; [on] these [other days], which do not have [an obligation] from the Torah outside the Mikdash, the rabbis decreed."
The gemara does not say that a mitzva applicable outside the Temple overrides Shabbat; in fact, such an assertion would contradict conventional halakhic logic. Clearly, the mitzva that overrides Shabbat is specifically the communal mitzva that focuses on the Mikdash. On the first day, this mitzva of the Mikdash finds expression even outside its boundaries, as opposed to on all other days of Sukkot. Therefore, Chazal did not cancel this special performance on the first day.
- The Distinction Between Lulav and Shofar:
- The Definition of "Mikdash" With Regard to Lulav:
The Rambam, in his commentary to the mishna (41a), writes that with regard to lulav the term "Mikdash" includes the entire city of Yerushalayim. The seven-day requirement thus applies not only in the Temple grounds, but throughout the city. In light of our approach, a solid basis for the Rambam's position appears in the mishna 42b. The mishna there records the edict issued requiring Jerusalemites on Shabbat to take their lulavim at home, rather than bringing it to the Temple Mount. If the Torah obligation in the "Mikdash" applies only to the Temple itself, then Chazal here effectively canceled the performance of this mitzva on Shabbat. If so, then we once again confront the Rambam's difficulty: why does lulav override Shabbat only before the destruction of the Temple, but not after? His answer, that after the destruction we no longer have "a Temple on which to depend," no longer resolves the problem, since Chazal canceled the performance of the obligation in the Mikdash. Both before and after the destruction, then, the obligation of the Mikdash was not observed.
We must therefore conclude that Chazal never considered canceling the mitzva in the Mikdash on Shabbat. After all, it is the communal performance that allows lulav to override Shabbat, and this communal performance occurs primarily in the Mikdash. Chazal merely changed the format of this mitzva's performance. Rather than bringing the lulav to the courtyard of the Temple, Jerusalemites would instead take it elsewhere throughout the city, which, for purposes of this halakha, has the status of the Mikdash.
In fact, this approach emerges from the straightforward reading of the mishna: "Lulav [is observed] six [days] or seven [days]." Meaning, when the first day of Sukkot falls on Shabbat, the mitzva was performed seven days; otherwise, it applied on only six days of Sukkot. The mishna makes no mention of this situation having changed, that the mitzva performance was later canceled on Shabbat, such that the mitzva never applied on more than six days. Apparently, the edict requiring people to take their lulavim in their homes rather than in the Temple constitutes an alternate form of the mitzva of lulav in the Mikdash, rather than a total cancellation of the mitzva.
[The full Hebrew version of this abridged article can be found in Alon Shevut 150 (Sefer Ha-yovel Li-Yeshivat Har Etzion).]
 Unless otherwise noted, all references to the Talmud are to Massekhet Sukka.
 This understanding emerges from Tosafot in Menachot (ibid.), as well as from the writings of the Rashba - chiddushim on Menachot, and Shut Ha-Rashba 4:28.
 This refers to the anshei ma'amad; see also the mishna, Pesachim 64a.
 See Rashi, 41a.
 The Meiri gives a different answer. In his view, the issue of divergent practices did not pose a problem of sufficient magnitude during the Temple era to cancel the mitzva performance on Shabbat. Only as a result of the destruction did a situation arise where a significant portion of the nation did not know when the court declared Rosh Chodesh.
 We may point to other mitzvot that likewise oblige the individual but serve to generate a communal performance, such as korban pesach (Rashi, Zevachim 13a).
One difficulty perhaps arising from this discussion relates to the Torah obligation of lulav on the first day of Sukkot in the aftermath of the Temple's destruction. If the individual performance serves merely to join the communal observance, then how can the Torah obligation apply to individuals in the absence of the Mikdash? Perhaps the communal obligation remains in effect even without a Temple by virtue of the fact that the entire nation observes this mitzva (though certainly this communal element is affected by the absence of a Mikdash).
In truth, however, even should we claim that the Torah intended for individuals to join specifically the Temple performance of the mitzva, we may reasonably assume that this personal obligation remains intact even when this goal becomes unattainable. It is characteristic of Halakha not to forego on a given framework even when we cannot realize the ideal purpose. Consider the Rambam's position concerning the counting of the omer, which is meant to count the days from the "omer" offering to the bread offering on Shavuot, as evidenced by its inclusion in Hilkhot Temidin U-musafin (which deals with sacrifices), rather than Sefer Zemanim (which deals with the festivals). Nevertheless, the Rambam maintains that this mitzva remains a Biblical obligation even nowadays, when this function no longer applies.
We may note another example, on the level of rabbinically-ordained obligation: Chanuka candles. Though the function of this mitzva is clearly "pirsumei nisa" (to publicize the miracle), some authorities hold that the obligation of lighting remains even when no potential for publicity exists, such as by day (Ravya 843) or during times of danger (when no minimum quantity of oil is required - Mordekhai, Shabbat 266).
A final example involves the halakhic principle of "eino ra'uy le-bila." Often, the Torah calls for the performance of a specific act in conjunction with a mitzva, but the mitzva can be satisfactorily fulfilled even without it, so long as the possibility exists of executing this act. Tosafot (Nidda 66b) ask, if the Torah did not render the given act indispensable for the performance of the mitzva, then why does it require the potential for its performance? Tosafot answer, "Since the Torah insisted that one must optimally perform this mitzva, we need that [the situation] lend itself to it, despite its not being indispensable, because otherwise, the mitzva would become entirely null and void, as it is impossible to perform." Meaning, halakha refuses to dispense with a given requirement entirely, even when the ideal to be realized through this requirement is not realized.
 See the Tanna Kama in Temura 14a, who indicates that public sacrifices override Shabbat. Rabbi Meir, by contrast, argues that the ability to override Shabbat depends not on the communal or individual nature of a given sacrifice, but rather on whether or not it must be brought on a specific day ("zemano kavu'a"). However, the Rambam, in the introduction to his commentary on Seder Kodashim, classified all sacrifices into four groups: communal, individual, communal but resembling an individual offering, and individual but resembling a communal offering. The Rambam thus implies that regarding the ability to override Shabbat and the laws of ritual impurity, one category may take on the properties of the other. It turns out, then, that essentially this ability depends on the communal or individual nature of the sacrifice, but the designation of a specific day for a given offering renders it "resembling" a communal offering. A thorough treatment of this point lies beyond the scope of our discussion.
 This is explicit in the aforementioned Yerushalmi, as well, which claims that without textual indication otherwise, lulav would override Shabbat on the first day only in the Mikdash.
 A similar example of this type of phenomenon may appear in a gemara adjacent to our discussio(44a), in the context of the mitzva of taking the arava (willow branch, observed nowadays on Hoshana Rabba). The gemara posits that this obligation as it applies in the Mikdash is either derived from a verse or transmitted through tradition as a "halakha le-Moshe mi-Sinai" (oral tradition dating back to Sinai). Outside the Temple grounds, however, this practice was established by the prophets (either as an outright obligation - "yesod nevi'im" - or by force of custom - "minhag nevi'im"). The Gemara then records Abayei's question as to why in the post-Temple era Chazal instituted that we take the arava only on the seventh day of Sukkot, as opposed to the lulav, which we take throughout the festival. It seemed to have been clear and obvious to Abayei that we take the arava on the seventh day of Sukkot after the destruction. He simply wondered why Chazal did not require this commemoration on the other days, as well.
For Rashi, however, this assumption, that we take the arava on the seventh day in the post-Temple era, was not obvious at all: "But one day, however, we do observe, as we say later regarding Rabbi Elazar Bar Tzadok, who lived after the destruction…" Why did Rashi feel compelled to draw historical proof for the application of this mitzva after the destruction? Why would this halakha have become obsolete after the Mikdash was destroyed?
Furthermore, other Rishonim actually reach such a conclusion, that the original institution of arava does not apply nowadays, and we observe this practice merely as commemoration. (See Ran, 22a and Tur, 664.) These Rishonim apparently understood that the prophets' institution of this mitzva outside the Mikdash required that people from all areas would participate in the mitzva of arava in the Temple. It therefore has no place nowadays, in the absence of a Temple, except as a commemorative act. The Rambam understood in a similar vein the relationship (on the level of Torah law) between the mitzva of lulav in the Temple and its obligation in other locations. We may even speculate that the prophets borrowed this very model from the Torah obligation of lulav in their institution of the mitzva of arava.
 Other Rishonim appear to take this position, as well. See Rabbeinu Chananel's text of the Gemara on 43a. See also Tosafot 43a, who ask why Chazal didn't require taking the lulav in one's home throughout the seven days.
 See Kesef Mishneh 7:13, who implies that we can "depend" on the Mikdash only when the lulav is actually taken there.