Musannaf Ibn Abi Shayba 9:924

Hatim ibn Isma'il narrated to us, from 'Abd al-Rahman ibn Harmalah, that he heard a man asking Sa'id ibn al-Musayyib. He said: "May I have physical contact with my wife while she is menstruating?" He said: "Place a garment between yourself and that part of her, then have physical contact with her."