[If] one brings his bull into another's yard with-out permission, and the other person's bull gores it, or the other person's dog bites it, he is exempt. [If] it gores the other person's bull, [the owner of the goring bull] is liable. [If] it falls into his pit and makes its water foul, he is liable. [If] his father or his son was in it, he pays ransom. But if he brings [it] in with permission, the owner of the yard is liable.  Rabbi says: In no case is he liable unless he accepts to watch.