Sanhedrin 72B

כאן ⁠– באב על הבן, כאן ⁠– בבן על האב.

Here, where the baraita teaches that if one is unsure about the burglar’s intentions it is prohibited for him to kill him, it is referring to a father who comes to rob his son. A father has great compassion for his son, and therefore it may be presumed that he will not kill his son if he resists. Accordingly, the son is prohibited from killing his father unless he knows for certain that his father has the intention of killing him. There, where the baraita teaches that if one is unsure about the burglar’s intentions it is permitted for him to kill him, it is referring to a son who comes to rob his father. Since a son has less compassion for his father, it may be presumed that he would be ready to kill his father if he resists. Therefore, the father is permitted to kill his son unless he knows for certain that his son would never kill him.

אמר רב: כל דאתי עלאי במחתרתא ⁠– קטילנא ליה, לבר מרב חנינא בר שילא. מאי טעמא? אילימא משום דצדיק הוא ⁠– הא קאתי במחתרתא! אלא משום דקים לי בגוויה דמרחם עלי כרחם אב על הבן.

Rav says: With regard to anyone who breaks into my house, I would kill him, as I would presume that he is ready to kill me, except for Rav Ḥanina bar Sheila, whom I would not kill. The Talmud asks: What is the reason that Rav excludes R' Ḥanina bar Sheila? If we say that Rav trusts him because he is a righteous person, this is difficult, as the case is one where he broke into his house, which indicates that he is not a righteous person. Rather, it is because he would say: I am certain that he would have mercy upon me just like a father would have mercy on a son.