Musnad Ahmad 1153:32

Muhammad ibn Fudayl narrated to us, from al-A'mash, from Tamim ibn Salamah, from 'Urwah, from 'Aishah, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to be in I'tikaf, and he would bring his head out to me from the mosque, and I would wash it while I was menstruating."