Musnad Abu Ya'la al-Mawsili 216:5

Abu Khaythama narrated to us, Jarir narrated to us, from al-Shaybani, from Abdullah ibn Shaddad, who said: Maymunah said: The Messenger of Allah (peace and blessings of Allah be upon him) used to have physical contact with his wives while they were menstruating. He would command them to wrap an izar (a garment covering the lower part of the body).