In describing the procedure for fulfilling the mitzva of the four species on Sukkot, the Shulchan Arukh (O.C. 651:2) writes that one takes the three species in his right hand, and the fourth – the etrog – in his left. This presentation might perhaps be intended to clarify not only with which hands the different species are to be held, but also the sequence. Meaning, as several commentators asserted, the Shulchan Arukh here might be intending to establish that one should first take hold of the bundle with the lulav, hadasim and aravot with his right hand, and only thereafter take hold of the etrog in his left hand.
The Magen Avraham (651:8), however, citing earlier writers, contends that to the contrary, one should first take hold of the etrog before taking hold of the other three species. Furthermore, the Magen Avraham rules that when one finishes using the four species, he should first put down the lulav, and only then put down the etrog. In other words, according to the Magen Avraham, when fulfilling the mitzva of arba minim, one must be holding the etrog whenever he holds the lulav (with the hadasim and aravot bound to it). The basis for this ruling, as the Magen Avraham writes, is the procedure for putting on tefillin. The Machatzit Ha-shekel explains that when we put on tefillin, we first place the tefillin shel yad on our arms before placing the tefillin shel rosh on our heads, and when we remove our tefillin, we first remove the tefillin shel rosh before removing the tefillin shel yad. Since the Torah first mentions the requirement of the tefillin shel yad before the tefillin shel rosh, the Sages inferred that the tefillin shel yad must always be worn whenever the tefillin shel rosh is worn. Hence, we must put on the tefillin shel yad first, and remove it last. By the same token, the Magen Avraham felt that as the Torah mentions the etrog first when listing the four species (“u-lkachtem lakhem…peri eitz hadar” – Vayikra 23:40), we must take hold of the etrog first and put it down last.
Interestingly, the Magen Avraham proceeds to note how this ruling affects the case of somebody who wishes to give his arba minim after fulfilling the mitzva to somebody else so he can also fulfill the mitzva. The first person, the Magen Avraham writes, cannot first hand his fellow the lulav, because his fellow will then be taking hold of the lulav before the etrog, but he also cannot hand his fellow the etrog first, because he must hold the etrog as long as he is holding the lulav. The Magen Avraham therefore writes that in such a case, the first person must place the four species on a table or other surface (placing first the lulav and then the etrog), from where his fellow will then take them, rather than hand them to his fellow directly. Later (651:12), the Magen Avraham proposes an alternative option, suggesting that the first person transfer the lulav to his fellow’s left hand, and then the etrog to that same hand. The second person then transfers the lulav to his right hand. Since the lulav must be held in the right hand and the etrog in the left, the second person is considered as having first taken hold of the etrog, because taking hold of the lulav with his right hand is halakhically insignificant.
Rav Yechezkel Landau (author of Noda Bi-yehuda), in his Dagul Mei-revava, dismisses the Magen Avraham’s ruling, rejecting the comparison between arba minim and tefillin. In his view, one should first pick up the lulav, and after completing the mitzva, one may put the four species down in whichever sequence he chooses.