Siman 347

In siman 389 it will be explained that for an ox that caused damage, the owners pay half-damage for a tam and full damage for a muad. If one handed it over to a guardian and it caused damage to the ox of another, the guardian pays according to the law of the owners, as written in siman 396. However, if the ox of a borrower damaged the ox of a lender, or that of a lender damaged that of a borrower, there are other laws regarding this which will be explained before us with the help of Heaven:

When one borrowed or hired a cow without specification, such that they did not speak regarding the manner of guarding, and similarly when he accepted upon himself to guard without specification, whether he is a shomer chinam or whether he is a shomer sachar, if the ox of the shomer or of the borrower and the hirer damaged the ox of the owner, whether it is a tam or whether it is a mu'ad, they pay nezek shalem. And the reason is that if it were damaged by the ox of another, they would be obligated to pay the entire damage, for behold, they are obligated in its guarding; and how is it possible that when the ox of the shomer himself damaged it, we would not obligate them in nezek shalem? And one cannot say that they only accepted the guarding such that it should not damage others, and not that it should not be damaged, for behold, presumably he accepted upon himself both that it should not damage and that it should not be damaged. Therefore, if they explicitly accepted only that it should not damage others and not that it should not be damaged—and even if they did not say explicitly that they did not accept that it should not be damaged, but since he said that he accepts it so that it should not damage, the meaning is that he does not accept upon himself that it should not be damaged, for if it were not so, he should not have specified at all, since without specification it is so [Sma]—then in this law, if his ox damaged it, in the case of a tam he pays chatzi nezek and in the case of a mu'ad he pays nezek shalem. And one cannot say that he should not pay at all since he did not accept that it should not be damaged, for certainly the guarded ox is no worse than an ox of the general public, for behold, if the ox of the shomer were to damage an ox of the general public, he would pay thus, and why should this ox be worse? And that which he did not accept upon himself that it should not be damaged, this refers to the law of guarding with an advantage over other damagers, but like any general damager he must pay, unless he stipulated thus explicitly that even if his ox damages it, he shall be entirely exempt.

And if the ox of the owners that was handed over to the shomer damaged the ox of the shomer, and the sharding was unspecified, whether it was a tam or a muad, the owners are exempt. For since he accepted its guarding, and had it damaged another's property the shomer would be liable, how is it possible that when it damages the ox of the shomer the owners should be liable? And if it damaged the ox of another, the shomer pays half-damage for a tam and full damage for a muad, for it is incumbent upon him to guard it so that it does not damage, as I wrote in siman 396. And if he accepted upon himself to guard it so that it would not be damaged, and not so that it would not damage, or if he said it should not be damaged and it is automatically implied that he accepted upon himself only this and not that it should not damage, as I wrote in section 2, and it damaged the ox of the shomer, the owners pay half-damage for a tam and full damage for a muad. And so too if it damaged the ox of another, the owners pay according to this law. For since he did not accept upon himself that it should not damage, they and others are equal in this law. And we do not say: granted that he did not accept upon himself that it should not damage, this applies when it damages others, but when it damages the ox of the borrower the owners should not be liable, for it is in his house and in any event it is incumbent upon him that his ox should not be damaged by it—for it is not so. Since he did not accept upon himself its guarding so that it should not damage, it is included by default even regarding the ox of the shomer, unless he stipulated so explicitly [Rosh, first chapter of Bava Kamma, siman 17].