Rashi on Exodus 22:12/רש"י על שמות כ״ב:י״ב

1אם טרף יטרף IF IT BE TORN IN PIECES — by wild beasts.

2יביאהו עד THEN LET HIM BRING WITNESSES that it has been torn in pieces by accident and he shall be freed from liability.

3הטרפה לא ישלם HE SHALL NOT PAY THAT WHICH HAS BEEN TORN — It does not say טרפה לא ישלם “one which has been torn he shall not pay for” — but it says “the torn one”, (the one mentioned here, viz., that which was torn without him being able to prevent it). Because there is a torn beast for which he has to pay and a torn beast for which he has not to pay. For an animal torn by a cat, a fox or a marten he has indeed to make restitution; but for one torn by a wolf, a lion, a bear or a serpent he is not liable to pay. But how do you come to make such a distinction (lit., who whispered to you to draw such a conclusion)? Because, you see, it states, “and if it die or be injured, or be captured”. Now what is the characteristic of natural death? One cannot save from it! Thus, also, the injury and the capture must be such that he was unable to save the animal from it (cf. Mekhilta).