What is the ruling on a man having intercourse with his wife at the beginning of her menstruation, with certainty [of her menstruation] established after the intercourse has ended?

If intercourse occurs during the usual menstrual period, but before the onset of blood, yellowish discharge, or brownish discharge, there is no harm in it. However, if it occurs after the onset of blood, yellowish discharge, or brownish discharge within the customary period, it is considered intercourse during menstruation. In this case, one must repent to Allah the Almighty, for He says: "And they ask you about menstruation. Say, 'It is a discomfort, so keep away from women during menstruation. And do not approach them until they are pure.'" Some scholars are of the opinion that a expiation of a dinar or half a dinar is due.