Musnad Abu Ya'la al-Mawsili 216:4

Abu Khaythama narrated to us, Sufyan narrated to us, from Manbudh, from his mother, who said: I was with Maymunah when Ibn Abbas entered upon her. She said, "O my son, why do I see you with your hair disheveled?" He said, "O Umm Ammar, my hair-comber is menstruating." She said, "O my son, and where is the menstruation from the hand? The Messenger of Allah (peace and blessings of Allah be upon him) used to enter upon one of us while she was menstruating, and he would place his head in her lap while she was menstruating. And one of us would bring him his prayer mat and spread it out while she was menstruating. O my son, where is the menstruation from the hand?"