Islamic Ruling on Intercourse During Menstruation
Intercourse during menstruation is strictly forbidden in Islam, and the person must repent and seek forgiveness.
According to the Quran, menstruation is described as something harmful and impure. Therefore, men are commanded to stay away from their wives during this time and not approach them for intercourse until they become completely pure.
A hadith explains that the Prophet (peace be upon him) would show closeness to his wives during menstruation, but without intercourse, and with proper covering.
From these sources, Islamic scholars have agreed that having intercourse during menstruation is strictly forbidden. This is a clear Islamic ruling and there is consensus on it.
If a person commits this act, there is no fixed financial penalty (kaffarah). However, he may be disciplined, and he must sincerely repent, seek forgiveness from Allah, and turn back to Him.
Some narrations mention giving charity of one دينار or half دينار, but scholars like Imam Nawawi have declared these narrations weak. Therefore, the correct fatwa is that no kaffarah is required, only repentance and seeking forgiveness.