It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever goes to his wife during her menstruation should give a dinar in charity; and whoever goes to her when the blood has stopped but she has not yet performed ghusl should give half a dinar in charity." All of this is narrated from the Prophet (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12082