Study Bava Kamma folio 45B with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
who says that a renter is considered like an unpaid bailee with regard to his responsibility for the rented item, let it teach that bailees are liable to compensate the owner, with the exception of an unpaid bailee and a renter.
And if it is in accordance with the opinion of R' Yehuda, who says that a renter is considered like a paid bailee, let it teach: With the exception of an unpaid bailee, as it in fact states; but it should also state that in a case where the oxen are forewarned, all of them are exempt with regard to
Rav Huna bar Ḥinnana said: In accordance with whose opinion is this baraita? It is in accordance with the opinion of R' Eliezer, who says that an ox has no sufficient safeguarding at all other than slaughtering it with a knife; i.e., there is no degree of safeguarding that exempts the ox’s owner,
Abaye said: Actually, the baraita is in accordance with the opinion of R' Meir; and it is as Rabba bar Avuh reversed the two opinions and taught: How does a renter pay? In other words, what is his degree of responsibility? R' Meir says: Like a paid bailee. R' Yehuda says: Like an unpaid bailee.
§ R' Elazar says: If the owner conveyed his ox to an unpaid bailee, if the ox caused damage, the bailee is liable to pay damages; but if the ox was injured, he is exempt.