First of all, we’d like to make it clear that in Islam we are not allowed to engage in sexual intercourse with our wives during their monthly periods. Allah says in the Qur’an, “They question thee (O Muhammad) concerning menstruation. Say: It is an illness, so let women alone at such time and go not in unto them till they are cleansed.” (Al-Baqarah: 222)
Thus, the husband has to abstain from having sex with his wife as long as there is menstrual bleeding.
however, if the wife assures that the blood has stopped and her period is over, then she has to perform ghusl (cleansing of the body) before she has intercourse with her husband or resumes offering Prayer and fasting.
Thus, when a woman’s period is over, she has to perform ghusl before having intercourse with her husband. After having intercourse you have to perform ghusl again to be pure for Prayer.
Elaborating on this, the eminent Muslim scholar, Dr. Sabri `Abder-Ra’oof Muhammad, Professor of Comparative Fiqh at Al-Azhar University and a member of the Supreme Council for Islamic Affairs stated that: “Almighty Allah says: “…Let women alone during mensesand go not in unto them till they are cleansed. And when they have purified themselves, then go in unto them as Allah hath enjoined upon you. Truly Allah loveth those who turn unto Him, and loveth those who have a care for cleanness.” (Al-Baqarah: 222)
Based on the above, it becomes clear that Allah has ordained that it is not permissible for the husband to have sexual relations with his menstruating wife. The time when the husband is allowed to resume this relation is after the flow of blood has ended and she has been purified by performing ghusl. This is clear from Almighty Allah’s saying: “so let women alone at such time and go not in unto them till they are cleansed,” which means after the menstrual blood stops. “And when they have purified themselves, then go in unto them as Allah hath enjoined upon you,” means that when the wife performs ghusl, then the husband can have intercourse with her.
Thus, it is impermissible for a husband to have intercourse with his wife before she performs ghusl and if he did so before she performed ghusl, he has to ask Allah for forgiveness. He can give charity as an expiation for his doing so.”