It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that a man came to the Prophet (peace and blessings be upon him) and said: I had intercourse with my wife while she was menstruating. He (peace and blessings be upon him) ordered him to give half a dinar in charity.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11648