What is the ruling on a husband having intercourse with his wife who informed him of the possibility of menstrual bleeding, and then the bleeding occurred on the same day after intercourse, and is expiation obligatory upon her?

It is forbidden to have intercourse with a menstruating woman in the vagina by consensus, and it is considered a grave major sin. If a Muslim believes that intercourse with a menstruating woman is permissible, he has disbelieved and apostatized. However, if he does so unknowingly of the menstruation, or of its prohibition, or under duress, then there is no sin upon him and no expiation. If he does so intentionally, knowing of the menstruation and the prohibition, and by his own free will, then he has committed a great sin and must repent. There are two opinions regarding the necessity of expiation; the most correct one is that there is no expiation upon him. However, if a woman claims to be menstruating and there is nothing to refute her truthfulness, then intercourse is prohibited.