הלכה על שמות 22:13

The Torah (Shemot 22:13-14) sets forth the rule of ba’alav imo, that a watchman or borrower is exempt from payment for loss of an item if he employs the owner of that item (see the Torah Temimah ad. loc. for explanations of this rule; one thought is that one cannot simultaneously be obligated to a person and have that person be obligated to him/her). The Shulchan Aruch (C.M. 346:13, based on Bava Metzia 97a) sets forth the rules regarding teachers and students in relation to the rule of ba’alav imo:

The commandment to judge the case of the borrower: To judge the case of the borrower, meaning to say a man who borrows any object or animal from his fellow. And borrowing is without a wage at all, but rather, he is doing a kindness for him to do him this favor. And if a disagreement breaks out between them about the matter, we must judge the law that is stated about this [upon] them, as it is written in this section (Exodus 22:13), “And if a man borrows from his neighbor, etc.” And regarding the law of the borrower, the Torah made [him] liable even for things of duress (out of his control) - as it is his responsibility: Since he borrowed it and did not put out any thing of his for it, behold he is like one who took out a monetary loan - who if something beyond his control occurred to him could not be exempt from [paying the] creditor, with the claim that it was duress. And about the matter that he is exempt if borrowing in the presence of the owners, we can say according to the simple understanding that the Torah did not make the borrower liable since the owner of the vessel or or the animal is with him - as since he is there, he will guard what is his. And even though the borrower is [still] exempt after the owners left [him], if they were there at the time of the borrowing - it is possible to answer about this that the Torah did not want to give different measures for its words and state that if the owners stay long, he will be exempt, but if [only] a little, he will be liable. [Instead,] the Torah commanded more generally that so long as the owners are there at the time of the borrowing, he will be exempt. And this is the reason that they, may their memory be blessed, said (Bava Metzia 95b), that if he was there with him at the time of the borrowing – even if he was not with him at the time of it breaking or dying – he is exempt; but if he was with him at the time of the breaking or the dying but he was not there at the time of the borrowing, he is liable. As the procedure depends on the beginning of the matter. And this very same reason suffices for us regarding that which he is also exempt if he rents [something] in the presence of the owners.