Bava Metzia, Chapter 3, Mishnah 2. The Mishnah continues discussing the laws regarding the four types of watchmen, and here it contrasts two of them: the renter and the borrower. This gives rise to a fascinating scenario where the cow's owner, the renter, and the borrower are faced with a single question: who pays for the cow that died, and who receives the payment?
The fundamental difference between the renter and the borrower:
The renter - exempt in cases of an unavoidable accident (oness). If something happened to the cow that was beyond his control, such as it being struck by lightning and dying, the renter can say: We had an agreement, I did not expect this, and there was nothing I could have done differently - and he is exempt from paying.
The borrower - liable even for an unavoidable accident. Even though it is clear that it was not in his power to prevent the lightning strike, since he enjoys full benefit from the cow without any compensation on his part, there is no room for excuses: he must reimburse the value of the cow he borrowed.
The case in the Mishnah:
Reuven is the owner of the cow, Shimon rents it from him, and Shimon lends the cow to Levi. While it is in the borrower's possession, lightning struck it and it died. A puzzling situation arises here: the renter can tell the owner that the cow died by an unavoidable accident and he is exempt, whereas the borrower is liable to pay, since the cow was harmed while under his watch.
And here lies the question: Who does the borrower pay? Is the payment given to the renter, from whom he borrowed the cow, or does the money pass along to the original owner - even though the renter himself is exempt from paying the owner?
The text of the Mishnah:
"Hasocher parah mechaveiro vehishilah le'acher" - the renter transfers the cow to a third party. It is worth introducing a well-known rule here: a watchman who transfers the item to another watchman is not permitted to do so, and by doing so he assumes full liability. We are forced to conclude, therefore, that our Mishnah deals with a case where the original owner gave explicit permission to the renter to lend the cow to that third party.
"Umeisah kedarkah" - the cow died in a normal manner, and not as a result of its work. This does not refer to a death that occurred during the course of the labor for which it was rented or borrowed, but rather a death that occurred on its own: it was struck by lightning, or any other cause unrelated to its use.
The two opinions in the Mishnah:
Tanna Kamma: "Yishava hasocher shemeisah kedarkah, vehashoel yeshalem lasocher" - the renter swears to the owner that the animal died by an unavoidable accident, and thereby is exempt from paying the original owner. The borrower pays the value of the cow to the person from whom he borrowed it, namely the renter, and the renter ends up profiting from the transaction.
Rabbi Yosi: "Keitzad halah oseh sechorah befarato shel chaveiro? Ela tachazor parah labealim" - how is it possible that the renter should make a profit from the owner's cow? Rather, the value of the cow passes from the borrower to the original owner.
The root of the dispute:
The point of dispute is at what stage the renter is exempted from his responsibility toward the owner:
According to the Tanna Kamma: The exemption takes effect immediately upon the cow's death, and the oath is merely to put the owner's mind at ease and appease him. Since the renter is immediately exempted from all responsibility, any profit that comes to him from the borrower - is his.
According to Rabbi Yosi: As long as the renter has not sworn to the owner that the cow is no longer in his possession and that it died a natural death, he is still liable toward him. Therefore, the owner can reject the oath, whether explicitly or implicitly, and say: I am not interested in your oath. The borrower is obligated to pay, and the cow is still mine, and you are not exempt from your responsibility here - therefore, the money passes from the borrower to the original owner.
The Halachah: The law follows the opinion of Rabbi Yosi. In this special case, we view the situation as if the original owner used the renter as a sort of agent and intermediary, as an emissary to lend the cow to the borrower with explicit permission - and therefore, the borrower must pay the money directly to the original owner.