We have learned that the Torah requires that a firstborn donkey be exchanged for a lamb that is given to the kohen(Shmot 13:13). According to the Mishnah (daf, or page 9a), if the lamb that was set aside to redeem the donkey were to die, it is permitted to benefit from the carcass.
The Gemara on today’s daf considers different possibilities regarding how to understand the case in the Mishnah:
- If it died in the possession of the kohen and the Mishnah is teaching that he is permitted to benefit from the animal, this would appear to be obvious, since it is his own money.
- If it means that it died in the possession of the owner and that the kohen is permitted to benefit from it, this too would appear obvious!
The Gemara concludes that we might have assumed that as long as the animal has not reached the kohen’s hands, the latter does not really possess it, so the Mishnah teaches that from the time that the owner has set it aside, it is already considered to be in the possession of the kohen.
This statement follows the opinion of the Hakhamim in the next Mishnah (daf 12b) that as soon as someone sets aside the lamb as the exchange for the donkey, even if it dies, the owner is not responsible to replace it. Tosafot goes so far as to rule that the blessing on performing this mitzvah – “Who has sanctified us with His mitzvotand commanded us to redeem a firstborn donkey” – is recited immediately when the lamb is set aside, even before it is given to the kohen.
The aharonim point out that one of the issues here is that it is forbidden to derive benefit from the donkey before the redemption takes place, so it would seem logical that we should view the lamb as replacing the donkey, and that the lamb should remain forbidden until it is accepted by the kohen. Since this is not the halakhah, clearly we view the lamb as becoming the kohen’s immediately upon being set aside.