Sahih Muslim
The Book of Menstruation (Kitab Al-Haid)
Book Number: 003 / Hadith Number: 584
'A'isha, the wife of the Apostle (may peace he upon him), reported: The Messenger of Allah (may peace be upon him) put out from the mosque his head for me as he was in I'tikaf, and I washed it in the state that I was menstruating.