The ruling on a son fasting on behalf of his father who killed someone by mistake

Question:
May Allah reward you, Honorable Shaykh. This questioner says: A man killed another man by mistake and paid the blood money to the heirs of the deceased, but he died without performing the expiation. What is required of his children after him? Do they fast, or do they expiate by feeding sixty poor people?

Answer:
There is no feeding in the case of the killer; there is no feeding for the killer. There are only two options: the first is freeing a slave, specifically a believing slave, and the second is fasting, fasting for two consecutive months. If he died without expiating and without fasting, then whoever wants to fast on his behalf, this will benefit him, if Allah wills, and it will clear his conscience, because this is a debt upon his conscience.
The Prophet (peace and blessings be upon him) said, "What do you think if there had been a debt upon your father?" Allah, Allah is more deserving of being paid. If a relative of his or one of his Muslim brothers fasts for him for two consecutive months, then that will clear his conscience. But it is not obligatory; it is not obligatory for these people to fast except by the door, except by the account to the deceased. Yes.