Question: Why would Rav Yisrael Salanter paskin that one can fulfill the mitzvah of lulav upon taking his friend’s lulav from his hands but can’t fulfill the mitzvah if he picked it up before dawn and was holding it after dawn, but rather he has to put it down and pick it up again?
A. Rav Yisrael Salanter poskined that if one picked up a lulav before dawn (alos hashachar) and it is still in his hands after dawn he still hasn’t fulfilled his mitzvah because the mitzvah is picking it up (or taking it) and the taking was at a time which one cannot fulfill the mitzvah yet.
B. The Binyan Shlomo (hilchos lulav, siman 48) is initially in doubt whether one can fulfill the mitzvah of lulav upon accepting it from his friend or whether he has to put it down and pick it up again. The question being whether the taking is the mitzvah and upon taking it was not his yet until it is in his hands or whether it being in his hands is the mitzvah and taking it is just the means of it getting into his hands. The Binyan Shlomo decided that even if the mitzvah is taking it one can still fulfill the mitzvah because upon taking it the transference of ownership and mitzvah happened at the same time.
C. Rav Yisrael Salanter does not hold of this logic which comes from a case by a “get” that a slave goes free as soon as he receive his freedom document in his hands though normally whatever a slave picks up automatically belongs to the owner but the logic of “the ‘get’ and the control of his hand come at the same time” prevents the owner from getting it. This logic is that really a slave can take whatever he picks up but it then goes to the owner but in this case the owner is not taking what should automatically come to him because he is showing he doesn’t want it.
D. In the case of the lulav this logic shouldn’t apply because one cannot start taking something which is not his so it is only given to him by the owner after it was taken so how could he fulfill the mitzvah?
E. Rav Yisrael Salanter really holds of a two part system of fulfilling this mitzvah, that the taking in part one of the mitzvah is in order to set up the main mitzvah of holding it.
Answer: Rav Yisrael Salanter really holds that the holding is the mitzvah but the means of holding it is the taking which is a step in the mitzvah so if it was taken before dawn it was not taken in order to fulfill the mitzvah since it was not at the time of the mitzvah but when being given the lulav to have, he is taking it as part of preparing to fulfill the mitzvah and when he has it in his hands and it is now his the main part of the mitzvah can be and is being fulfilled.