If a Man Swears to Divorce or Free Someone Over an Act and Then Forgets and Does It, What Is the Ruling?

Hazrat Hasan (may Allah be pleased with him) used to say that if a person says, "If I enter so-and-so's house, my wife is divorced," and then he forgetfully enters that house and enters there without knowledge, then this will be like entering deliberately. However, if while taking the oath he had made an exception for forgetfulness, etc., then divorce will not take place.

Hazrat Abdullah bin Uthman (may Allah have mercy on him) narrates that my brother Umar bin Uthman (may Allah have mercy on him) swore an oath that if he drank from the hand of such-and-such slave-girl within a certain period, she would be free. Then, before the period was completed, he forgot and drank from her hand. I asked Hazrat Ata, Hazrat Mujahid, Hazrat Saeed bin Jubair, and Hazrat Ali (may Allah be pleased with them all) about this matter, and all of them said that she is free.

It is narrated from Hazrat Ata (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: Allah Almighty has removed three things from my Ummah: mistake, forgetfulness, and the action that is done under compulsion.

20169 - He said: Ata' said: It has reached me that the Messenger of Allah ﷺ said: "Indeed, Allah has pardoned for my ummah three things: mistakes, forgetfulness, and what they are compelled to do." (1).

Hazrat Zuhri (may Allah have mercy on him) and Hazrat Umar bin Abdul Aziz (may Allah have mercy on him) used to consider a divorce given by mistake as valid.

20171 - From Ma'mar, from Sa'id ibn Abd al-Rahman, from (Umar ibn) (1) Abd al-Aziz, (that both of them) (2) used to consider the divorce of forgetfulness as binding.

The companions of Abdullah bin Masood (may Allah be pleased with him) used to consider this divorce as effective.