It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said concerning a man who has intercourse with his wife while she is menstruating: "He should give a dinar in charity, and if he cannot find it, then half a dinar."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11871