Musannaf Ibn Abi Shayba 7:227

Abu Bakr narrated to us, he said: Sharik ibn Abdullah narrated to us, from Khusayf, from Miqsam, from Ibn Abbas, attributing it to the Prophet (marfu'), he said: A man came to him and said: "I had intercourse with my wife while she was menstruating." He said: "Give half a dinar in charity."