What is the ruling on a husband having intercourse with his wife who doubts her purification after menstruation? Is there any expiation or sin upon her for not being certain of her purification? And is there anything upon the husband?

A woman recognizes purity by one of two signs: dryness or the white discharge (al-qassah al-bayda’).

If she sees either of them, ghusl (ritual bath) and prayer become obligatory, and it is permissible for her husband to have intercourse with her.

Yellowish or brownish discharge after purity during the time of menstruation is considered menses. Otherwise, it is not.

If she doubts her purity, the default is the continuation of menstruation. She should not perform ghusl until she is certain of her purity.

If her customary period changes, the new custom is considered valid.

If you are certain of your purity and what you saw was merely a doubt or a whisper (waswasa), do not pay attention to the whisper; the intercourse is valid.

If you performed ghusl while doubting the occurrence of purity, this ghusl is not considered valid. Both of you must repent and seek forgiveness for engaging in intercourse during menstruation. It is recommended to offer expiation of one dinar or half a dinar, with a choice, according to the Hanbalis, while the majority of scholars do not consider it obligatory.