Shiur #16: Leaving Food on the Fire and Covering Knobs

  • Rav Yosef Zvi Rimon


By Rav Yosef Zvi Rimon


Dedicated in memory of 
Joseph Y. Nadler z”l, Yosef ben Yechezkel Tzvi


Shiur #16 – Leaving Food on the Fire and Covering Knobs



May one leave uncooked dishes on the fire on Friday?


Is it permissible to put dishes on a gas burner if it is covered by a blech (a plate of tin)?


Which dishes can one put on an electric hot plate before Shabbat? May one put cold soup on it if it will not heat up before Shabbat commences?




As we discussed in the previous shiur, one may not leave on an open fire a dish that has begun cooking but has not yet reached the level of ma’akhal ben Derusai.  As we have explained, the prohibition stems from the concern that one may come to stoke the coals.  In our modern reality, this translates to a concern that one may turn up the heat.  In light of this, the Sages allow one to leave a pot on the stove when the coals are swept away or sprinkled with ashes, making the stove respectively gerufa or ketuma.


One practical solution has been the blech (“tin” in Yiddish), a flat piece of metal (nowadays, usually aluminum) that covers the burners on a range; more recently, an electric hot plate has become popular, designed with room for several pots and no knobs (known in Modern Hebrew as a “plata”). 


What is Ketuma?


In order to explain this, we must first understand the reason that one is allowed to leave dishes on a stove that is ketuma (if ashes are poured on the coals, rendering the fire less effective).  The concept of a stove that is gerufa is easily understood; once the coals have been swept away, it is impossible to stoke them!  But why is one allowed to leave a pot on a stove if its coals have been sprinkled with ashes?  One can still stoke the coals to raise the temperature!




Rashi (36b s.v. O) explains:


“Or sprinkles ashes upon it” — on top of the coals in order to cover and cool them. 


This indicates that sprinkling reduces the stove’s heat.[1]  This is also what the Tur (ch. 253) writes: “One covers the coals with ashes to reduce its heat.”  This is also what the Shulchan Arukh (253:1) writes.  Why is the reduction of heat efficacious to allow shehiya?  It appears that one who reduces the heat of the stove demonstrates by this that he is not eager for bishul, so that there is no concern that one will come to stoke the coals.  This is what the Rambam (3:4) writes:


Accordingly, retention is permissible if one has removed the coals or covered the coals with ash… because one puts it out of his mind.  Hence, no decreed is made lest one rake the coals.


Ramban, Rashba


According to this view, some Rishonim (Ramban, Rashba, Ran, et al. 36b), that there is no need for actual sprinkling, but rather spreading some ashes over the coals; by this, one demonstrates that he is not eager for bishul, and he does not care about the coals’ heat.  As the Rashba puts it, “Since one sprinkles a bit, it is clear that one gives up hope, and one does not want to stoke it.”  This is also the implication of the Gemara (37a): even putting thin chips from the combing of flax on top of coals is considered sprinkling.




The Remakh (3:4, cited by Kesef Mishneh ad loc.) explains the aim differently:


The correct reason is that one makes a noticeable sign, such as sweeping or sprinkling, and then one will not come to stoke.


In his view, the sprinkling does not demonstrate that one puts it out of his mind, but to be a sign and a reminder; should a person come to stoke the coals on Shabbat, he will see the ashes and recall that there is a prohibition.[2]


Covered Fire


In light of the different reasons for permitting retention on an oven that is ketuma, we may go back to the question with which we opened: is one allowed to leave a dish on a flame covered with a blech?  Apparently, we should answer this question according to the first two reasons.  According to the Remakh, the sprinkling serves as a sign and reminder not to stoke the coals; it makes sense that covering the fire is a good reminder so that one will not stoke the coals and turn up the fire (even though one may dispute this and say, that the reminder must be attached to the knobs by which one turns up the fire and not the fire itself).  Also, even according to the view of most Rishonim that sprinkling ashes on the coals indicates that one is diverting his attention from the cooking, we have seen that according to many Rishonim it is enough to have a symbolic act such as this that expresses the diversion of one’s attention, and according to this, it makes sense that covering the flame is enough. 


However, one may say that reducing the heat alone expresses the diversion of one’s attention from bishul, as is implied by the words of Rashi and Tur, and according to this, it makes sense that covering the fire does not express the diversion of one’s attention.  Indeed, one does not reduce the heat meaningfully, and naturally it does not help to make the stove gerufa or ketuma. 


The Chazon Ish (37:9, 11) writes to be stringent about this, and he offers a proof to this from Rashi’s words.  The Gemara (37a) states:


They queried: “What of leaning against it?  On the inside and on top of it is forbidden, but leaning against it may be permitted; or perhaps, there is no difference?”


From this passage, it arises that the doubt relates only to retention near a stove, but inside (their stoves were quite deep) or on top of it, there is no doubt that shehiya is forbidden.  What is the meaning of “on top of it?  Rashi explains:


“On top of it” — the thickness of its rim or a cover over its hollowness. 


In other words, this refers to placing the pot on a cover over the stove as well.  According to this, the Gemara says this explicitly, there is no allowance to leave the dishes on a covered stove, and the cover does not help to define the stove as gerufa or ketuma.  The Tur (ch. 253) explains the words of the Gemara with language similar to that of Rashi.[3]


However, the Mordekhai (80a) indicates that if a stove is covered with an empty, inverted pot, it is considered gerufa, “because the pot seals the stove,” and his words form the halakhic ruling of the Shulchan Arukh (253:3).  The Chazon Ish (37:9) relates to this in the following way, and he claims that a tin cover is worse than an inverted pot:


Behold, that separation of an empty pot is efficacious because it appears that it is an alteration, for this is not the way of cooking (derekh bishul).  Moreover, it also reduces the heat considerably. However, using the cover, which is customary and does not reduce the heat too much, is included in the category of “on top of it.” 


Chazon Ish


According to this, covering a stove with a blech is not enough in order to express the diversion of one’s attention from bishul, since this act is not so exceptional and it does not reduce the heat too much, as opposed to covering the stove with an inverted pot, which is considered an unusual act that reduces the heat radically.  In addition, the Chazon Ish (37:11) writes:


In our holy land, the custom is to put the pot on a burner, and the flame is underneath, below the bottom of the pot, but this is like an unswept stove, and even if there is a metal plate and the pot is on the plate, in any case, it is not considered like putting an empty, intervening pot on a stove.  This is only placing a cover on the stove and putting a pot on the cover, which is considered “on top of it,” as I have written above.


Most Authorities


On the other hand, Rav Moshe Feinstein writes (OC, Vol. I, ch. 93) that covering the fire with a blech makes it ketuma.  According to him, what Rashi and the Tur write, that the cover does not help to make the stove ketuma, is only relevant when applied to the Talmudic ovens, as one would cook on their covers; our blech, on the other hand, is unusual, so it makes the stove ketuma.


This is also what Shevet Ha-Levi writes (Vol. I, ch. 91), and he adds that the authorities indicate there is no need specifically to reduce the heat, but every act that differs from the regular way of cooking becomes a sign and reminder in order to make the stove ketuma:


Certainly, the simple meaning of the glosses of the Mordekhai shows that the very fact that the fire is covered makes it allowed, even though the heat remains as it was at first, because for the issues of sweeping and sprinkling, the heat is immaterial, since the principle exists because of the concern of stoking…


Thus, there is certainly no question to be asked about the cover of the stove based on what Rashi and the Tur write, that it is not efficacious, for there it is the regular cover that is put on the stove every day…


In any case, when one puts an empty pot on the stove, it is not the usual way for it to be there and it is permissible.  This item that does not belong there and covers the flame makes it like it was swept and sprinkled; if so, it is the law for the large plates that they put on the burner; they are not at all like the regular cover of the stove. 


In addition, in Tashbetz Katan (ch. 27) we find that the Maharam allows putting a dish on a board upon the oven even on Shabbat itself, as written by the Magen Avraham (253:31) and Mishna Berura (253:81), and this should be similar to a blech-covered stove.  This is how Rav Neuwirth rules (1:18), that a blech-covered stove is considered ketuma. 


In Yabbia Omer (Vol. VI, OC, 32:5), Rav Ovadya Yosef adds a reason to be lenient, and he writes that it may be that the Sages make no decree except concerning a coal-fueled stove, which usually fades over time, for we are concerned that a person will stoke the coals in order to maintain the temperature, but in our stoves, in which the temperature is constant, the Sages’ concern that a person will raise the temperature is not applicable.

Thus, for example, the custom is to relate to a blech-covered flame as a ketuma, whether for issues of shehiya or hachazara, which we will deal with below.


Hot Plate


When it comes to an electric hot plate, there is even more of a reason to be lenient, because it is not designed at all for bishul, and one cannot turn its heat up or down.  Thus, it makes sense that the Chazon Ish concedes that it is a ketuma (Brit Olam, Dinei Shehiya Ve-chazara, no. 26; Az Nidaberu, Vol. VIII, ch. 16.  However, see the opposing view of Orechot Rabbeinu, Vol. I, p. 10).[4]


One should stress that this relates to retaining a dish on a plata before Shabbat.  When it comes to putting the dish on the plata on Shabbat itself, there is another dispute of halakhic authorities related to hachazara, which we will deal with in a future shiur.





Instead of covering the fire itself, is it enough to cover the knobs that we use to regulate the flames?


Apparently, this is related to a dispute that we have seen about the reason to allow leaving food on a sprinkled stove: if the sprinkling is supposed to be a mark and a reminder not to stoke the coals, covering the knobs is an excellent sign, because every concern about modern stoves is that a person may turn up the flames using knobs, and if they are covered, this is an excellent reminder not to touch them.  On the other hand, if the sprinkling reduces the temperature and expresses the diversion of one’s mind from cooking, then the covering of the knobs, which does not change anything in the process of cooking, does not make the stove ketuma. 


Covering Knobs Is Not Sprinkling


Rav Feinstein understands (Iggerot Moshe, OC, Vol. I, ch. 93) that this is a secondary possibility, that a person must demonstrate that he is not preoccupied with bishul, and there is no need for a great fire.  Therefore, Rav Feinstein rules that covering the knobs does not help:


If one only covers the knobs and not the fire, this will not help, because the essence is that one must show that his intent is solely to lower the temperature, which is more readily apparent when one covers the fire.


In his view, one must do an action specifically to the fire itself, an act that expresses one’s desire to reduce the fire.[5]


However, even if covering the knobs is not considered sprinkling, it may be that one should be lenient for a different reason.  The Gemara (18b) determines that one may leave food in an unswept oven, if the door of the oven is daubed with clay.  What does daubing with clay accomplish?


Daubing — Dispute of Rishonim


Rashi (ad loc., s.v. Sharik) explains that in order to open the oven door and to stoke the coals, there is a need to break the clay, and before one can manage to break it, he will remember that it is forbidden to stoke the coals.  On the other hand, the Rambam (3:13) writes that the allowance is applicable only to those certain types of meat that may be damaged by the wind: we are not concerned that the person will exert effort to remove the clay, to open the oven and to stoke the coals, since this act damages the meat.  According to Rashi, this allowance applies to every food that is found in an oven that is sealed with clay; according to the Rambam, the allowance is limited to a certain type of meat alone.  


From this argument, there may be halakhic ramifications for our issue: may one leave food on a gas range, covering the knobs and taping the cover, so that in order to turn the knobs, one must take the cover off?  According to Rashi, it makes sense that the matter will be allowed, since the case is similar to that of an oven daubed with clay, while according to the Rambam, it makes sense that this would be forbidden: the lenient view about a clay-daubed oven is limited to meat that will be damaged by wind. 




The Shulchan Arukh (254:1) rules in accordance with the view of the Rambam, while the Rema rules to be lenient, following the view of Rashi:


There are those who… believe that in an oven daubed witch clay, everything is permitted.




According to the Rema, the Chazon Ish writes (36:3, 38:2) that if we install a lock on the door of the oven and lock the door, there is no prohibition of shehiya (even if it has not yet reached ma’akhal ben Derusai).  Apparently, one may say that if one does not merely cover the knobs, but one also seals the cover in a way that makes it impossible to change the height of the flame without removing the cover,[6] Ashkenazim may be lenient and consider the stove ketuma, even if the stove is not covered.[7]  It is best to write “Shabbat” on the note that one tapes to the knobs. 

However, generally it is accepted that one should be stringent about two things: to cover the gas (so that there will be a mark upon the body of the fire, as it were) and even to cover the knobs (this is the significant element by which one may violate the prohibition).  However, by the letter of the law, one may be lenient after covering the flame alone, and in a case of need, one may be lenient after covering the knobs alone, if one seals the covering.  For this matter, there is a significant ramification concerning shehiya in an oven, as we shall see in a coming shiur.




To conclude, one may make a gas range ketuma (allowing one to retain upon it a dish that has started to cook but has not yet reached ma’akhal ben Derusai) by covering the flames.  One should cover particularly the fire, not the knobs, since we need a reminder upon the body of the fire; however, it makes sense that if one seals the knobs, one may suffice with this (at least for Ashkenazim), because then we need to do an action in order to turn the knobs, and this matter will remind the person that today is Shabbat.  Generally, people are stringent and cover both the flames and the knobs, but in terms of the law, there is a reason to be lenient after either covering the flame or sealing the knobs.




[1]      It may be that we should offer a proof from Rashi himself, because according to the simple meaning, the mishna is not dealing with shehiya, but rather with hatmana (Ramban, Rashba, et al. also explain in this way); if so, one should cool the coals, so it is not considered something that adds heat.

[2]      The Remakh challenges the explanation of Rambam and most Rishonim: how can one say that sprinkling shows that one has diverted his attention from the dish?  One wants to eat it for supper, so diverting his attention is untenable!  It makes sense that the Rambam and other Rishonim will respond that a person diverts his attention from the dish; however, one diverts his attention from heating the dish and shows that he is not that concerned with the question of when the bishul will conclude, so that one does not try to accelerate the process.  The views of the Rishonim do require further analysis, but this is not the place for it.

[3]      The Bei’ur Halakha (253:1, s.v. Litten) cites their words and writes that the words of the Rambam indicate that he argues with them, and in his view, only on top of the fire itself is there a problem, but a covered stove is considered gerufa or ketuma, since one diverts his attention from bishul.  Indeed, the Bei’ur Halakha is troubled by the view of the Rambam about this issue, concluding that it requires further analysis.

[4]      In leaving dishes on a plata, there may be an issue of hatmana, according to the view that partial insulation is considered hatmana. We will deal with this issue in a future shiur.

[5]      According to his view, when one covers the fire, there is no need to cover the knobs, though he writes that there is a preference for this ab initio.

[6]      According to Rashi (ad loc., s.v. Ve-tocheh) it arises indeed that there must be some effort necessary to remove the clay, and this arises from the words of the Bei’ur Halakha (254:1, s.v. Af al pi).  However, from the above-mentioned words of the Chazon Ish, it appears that there is no need for this level of effort; the necessity of opening a lock and the like is enough to remind one of the situation and to ensure that one will not come to stoke the coals.

[7]      However, Rav Feinstein writes that it is not enough to cover knobs, as we have seen above; however, we are dealing here with a better solution: not only covering the knobs, but sealing them.  This is not a reminder but instead it is a roadblock preventing one from stoking the coals: one who will come to stoke the coals (to turn up the fire) should need to do something and remove the seal; in the meantime, he will recall the prohibition.  There is an oral tradition to be lenient, as has been told to me in the name of Rav Joseph B. Soloveitchik.  (Rav Avishai David told me this, but it is not clear to me whether Rav Soloveitchik allowed this with any covering or only with a sealed covering.)

As for removing the knobs, Rav S.Z. Auerbach (Minchat Shelomo, Vol. II [5759], 34:21) poses a question: if one removes the knobs, so that it is impossible to change the height of the flames without putting them back on, is this considered a clay-daubed oven?  Logically, if we are lenient about knobs that are sealed, all the more so we should be lenient about knobs that have been totally removed, and this is how Rav Wosner rules (cited by Orechot Shabbat, p. 516).