Bava Kamma 54B

הא שור שהוא פקח ⁠– פטור?

The Talmud asks: But can it be inferred that if an ox that is of standard intelligence fell into a pit, the owner of the pit would be exempt?

אמר רבי ירמיה: לא מיבעיא קאמר; לא מבעיא שור שהוא פקח ⁠– דחייב; אבל שור חרש שוטה וקטן, אימא חרשותו גרמה לו, קטנותו גרמה לו, וליפטר; קא משמע לן.

R' Yirmeya said: The Mishnah is speaking utilizing the style of: It is not necessary, and should be understood as follows: It is not necessary to state that if an ox that is of standard intelligence fell into a pit, that the pit’s owner is liable. But with regard to an ox that is deaf, an imbecile, or very young, say that it was not due to the pit alone that it fell in, but its deafness caused it to fall in or its young age caused it to fall in, and the owner of the pit should be exempt. Therefore, it teaches us that he is liable in these cases as well.

אמר ליה רב אחא לרבינא, והתניא: נפל לתוכו בר דעת ⁠– פטור. מאי, לאו שור בר דעת? אמר ליה: לא, אדם. אלא מעתה, אדם בן דעת הוא דפטור, הא לאו בן דעת הוא ⁠– דחייב? ״שור״⁠ – ולא אדם כתיב!

Rav Aḥa said to Ravina: But isn’t it taught in a baraita: If a living being that is mentally competent fell into a pit, the owner is exempt. What, is it not referring to an ox that is mentally competent? Ravina said to him: No, it is referring to a person. Rav Aḥa challenges this response: If that is so, you should then infer that it is only for the injuries of a person who is mentally competent that he is exempt, but if one is not mentally competent, is the halakha that he would be liable? But the term “an ox” is written in the Torah as causing liability, and not a person.