What is the expiation for an oath of divorce regarding the wife not entering any of her relatives' homes, knowing that she has only entered the homes of her father and grandfather, and now she wishes to visit the home of her recently married sister and the homes of her sick relatives?

The majority of scholars hold that if a man swears an oath by divorce and then breaks it, his wife is divorced, whether he intended to enact the divorce or merely to threaten. The fatwa issued adheres to the view of the majority. The husband cannot retract an oath sworn by divorce according to the majority; therefore, if he permits his wife to visit those he swore she would not visit, his permission does not prevent her divorce. Accordingly, if the wife visits her relatives whom she was forbidden to visit, she is divorced. If this divorce does not complete the triple divorce, you may take her back before her waiting period (iddah) expires, and the oath is dissolved after reconciliation.

As for the view of Sheikh al-Islam Ibn Taymiyyah, if the oath was intended as a threat and you did not intend to enact divorce, then divorce does not occur when the wife visits, but you are liable for an expiation for breaking an oath (kaffarat yamin). However, if you intended divorce, you may retract it according to Ibn Taymiyyah and those who agree with him.

The permissible oath is to swear by Allah the Almighty. Swearing by divorce is among the oaths of the wicked and may lead to undesirable consequences.