(Mishnah): If a person borrowed a cow (on condition that) he borrowed it for half-day and rented it for half-day or that he borrowed it for today and rented it for tomorrow or he borrowed one cow and rented one cow...

If the lender says that it was the borrowed one that died, or on the borrowed day or at the borrowed hour; if the other one says that he does not know, the borrower is liable.

If the renter says that it was the rented one that died, or on the rented day, or at the rented hour; if the other one says that he does not know, the renter is exempt.

If one says that it was borrowed and the other says that it was rented, the renter must swear to this.

If both say that they do not know, they should divide it.

(Gemara) - question: If he borrowed it today and rented it tomorrow, what is its status in the night time in between the two?

Answer #1: It is the way of cows to sleep in the possession of their owners (i.e. it is the norm for a cow to be returned immediately after a day of use). Here, because he had rented for the next day, he had not returned it in the evening. Therefore, it is treated as if it was (still) borrowed (when it died) and he is liable.

Answer #2: It is not the way of cows to sleep in the possession of their owners. Therefore, it is treated as if it was rented (when it died) and he is exempt.