Musannaf Ibn Abi Shayba 1:2109

Ibn Numayr and Ya'la ibn 'Ubayd narrated to us, from al-A'mash, from Tamim ibn Salamah, from 'Urwah, from 'Aishah, who said: "I used to comb the hair of the Messenger of Allah (ﷺ) while I was menstruating, and he was in i'tikaf."