The eighth perek of Massekhet Bava Metzia, ha-Sho’el et ha-Parah, begins on today’s daf, and its focus is on the responsibilities of someone who rents (sokher) or borrows (sho’el) an animal or an object from his friend. Borrowing and renting are qualitatively different than acting as a guard whose job is to watch something for his friend, since the borrower or the renter receives the object with the understanding that he will use it. Thus the owner accepts the fact that there will be normal wear-and-tear on the object. At the same time, the level of responsibility that the borrower or the renter takes upon himself will be greater than that accepted by a normal guard or watchman.
The Torah appears to obligate a borrower – she-kol hana’ah shelo – who derives only benefit from this relationship – in all cases, even in cases of ones where an accident takes place that is beyond his control (see Shemot 22:13-14). The one exception is a case of be’alav imo – when the owner of the animal is there together with the borrower, then the borrower (and, according to the Gemara, all other shomerim, as well) will not be responsible. Defining the situation that is considered to be be’alav imo is one of the tasks of the first Mishna in the perek.
According to the Mishna, the rule that the borrower will not be obligated to pay damages for an animal as long as the owner is with him, applies only if the owner was hired to provide services before the animal was borrowed or if both relationships were created simultaneously. If, however, the animal was borrowed first and the owner was only hired later on, then the borrower will be held liable for anything that happens to the animal.
The Torah law with regard to a sokher is unclear (see Shemot 22:14), and the tanna’im disagree as to his level of responsibility, although all agree that the Torah intends to free the sokher from the high level of responsibility that rests on a sho’el.