Maqsim bin Bajra مقسم بن بجرة · Marriage (Kitab Al-Nikah)

Maimunah daughter of Al Harith said “When the Apostle of Allaah(ﷺ) intended to associate and lie with any of his wives who was menstruating, he ordered her to wrap up the lower garment(loin-cloth) and then he had association with her.

The Prophet (ﷺ) said about a man who has sexual intercourse with a menstruating woman: He should give one or half dinar as sadaqah.