Mishnayos Bava Kamma Perek 4 Mishnah 6

שור שהיה מתחכך בכותל וכו' – is exempt from the death penalty, but if if was forewarned, as in the case that it was forewarned to rub itself against walls and to knock them over on humans, and it rubbed itself against the wall for its pleasure and it fell on a human being and he died, the ox is exempt from the death penalty but the owners pay the ransom. The ox is exempt from the death penalty, as it is written (Exodus 21:29): “[If, however, that ox has been in the habit of goring, and is owner, though warned, has failed to guard it, and it kills a man or a woman -] the ox shall be stoned, and its owner, too, shall be put to death.” As it is with the death of the owners, so too with the death of the ox. Just as the owners are not liable if they killed a person, until they killed him with intent, so too, the ox is not liable until it kills with intent. And the owners pay ransom, as it is written (Exodus 21:30): “If ransom is laid upon him, [he must pay whatever is laid upon him to redeem his life],” for the Torah could have stated