He—may Allah Most High have mercy on him—was asked:

A man found another man with his wife and killed her, then repented after her death. He had young children. When one of the two grew up, he wished to offer the expiation for killing. Unable to afford to free a slave, he wished to fast for two consecutive months.

Is expiation obligatory for the killer? Is it valid for his child to perform it on his behalf? If the child is female and menstruates during those two months, does that interrupt the required continuity? If she considers it most likely that her menstruation will end at a particular time, must she abstain from the things that invalidate fasting, or not?

He replied:

Praise be to Allah. If he found them committing the indecent act and killed her, he bears no liability before Allah according to the stronger of the two scholarly opinions. This is also the stronger of the two opinions in Ahmad’s school, even if he could have stopped the man from having intercourse with her by speaking to him. For it is established in the two Sahīh collections that the Prophet, may Allah bless him and grant him peace, said:

“If a man were to peer into your house and you put out his eye, you would bear no liability.”

And:

“A man once peered into his house, and he began aiming a pointed comb at the man’s eye; had it struck him, it would have put out his eye.”

He also said:

“Seeking permission to enter was prescribed only to prevent people from looking in.”

Yet he could have stopped him by speaking to him. A man came to Umar ibn al-Khattāb, may Allah be pleased with him