For the source text click/tap here: Bava Kamma 37
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An ox that is a mu’ad to damage other oxen but no other animals, or if it is a mu’ad to gore people but not animals, or if it is a mu’ad for children but not for adults, for whatever it is a mu’ad, he (its owner) pays full damages, and for whatever it is a tam, he pays half damages.
They asked Rabbi Yehudah: What happens if an animal is a mu’ad for Shabbos and not for the weekdays? Rabbi Yehudah told them: For damages done on Shabbos, he pays full damages, and for damages done during the week, he pays half of the damages.
Rashi explains the rationale as follows: Since the animal does not work on Shabbos, we may assume that it becomes arrogant and therefore it acts upon its destructive urges and begins to gore or it is the only day on which the animal is not tethered to something, and the freedom that it has may lead it to out-of-the ordinary acts of violence.
Tosfos cites a Yerushalmi which explains differently: The animal’s Jewish owners tend to wear different clothing on Shabbos. The ox, unable to recognize its owner, becomes confused and decides to gore.
We compare ox vs cow and buffalo.