Is a wife's fast valid if her husband has intercourse with her while she is forgetful of her fasting, and he knows that she is fasting?

If a wife is fasting an obligatory or supererogatory fast with her husband's permission, it is not permissible for him to break her fast. He must repent and seek forgiveness if he does so.

However, if she fasts a supererogatory fast without his permission, he has the right to make her break it, based on the Prophet's (peace and blessings be upon him) saying: "It is not lawful for a woman to fast a day while her husband is present except with his permission."

The wife's fast is valid, and there is no sin upon her nor expiation, because she was forgetful. A person who has intercourse forgetfully is treated the same as one who eats or drinks forgetfully.