The Prophet (ﷺ) said about a man who has sexual intercourse with a menstruating woman: He should give one or half dinar as sadaqah.
Sunan Abi Dawud Book 12, Hadith 123
← Previous Hadith 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.

Sunan Abi Dawud Book 12, Hadith 122 Next Hadith → If a man has sexual intercourse (with menstruating woman) during her bleeding, he should give one dinar as sadaqah, and if he does so when bleeding has stopped, he should give half a dinar as sadaqah.

Sunan Abi Dawud Book 12, Hadith 124