The Prophet ﷺ would lean his head toward me while he was in seclusion in the mosque, and I would wash it while I was menstruating.
أخبرنا عمرو بن علي قال حدثنا يحيى قال حدثنا سفيان قال حدثني منصور عن إبراهيم عن الأسود
كان النبي ﷺ يومئ إلي رأسه وهو معتكف فأغسله وأنا حائض
Bukhari narrated it in the Book of Itikaf, chapter "The One Performing Itikaf Washing Himself," hadith 2031, from the hadith of Sufyan Thawri. Muslim narrated it in the Book of Menstruation, chapter "The Permissibility of a Menstruating Woman Washing Her Husband's Head," etc., hadith 297, from the hadith of Mansur, through him. It is also in Al-Kubra, hadith 269.