Sahih Al Bukhari (296)

عن عروة أنه سئل: أتخدمني الحائض، أو تدنو مني المرأة وهي جنب؟ فقال عروة: كل ذلك علي هين، وكل ذلك تخدمني، وليس على أحد في ذلك بأس، أخبرتني عائشة: أنها كانت ترجل، تعني رأس رسول الله صلى الله عليه وسلم، وهي حائض، ورسول الله صلى الله عليه وسلم حينئذ مجاور في المسجد، يدني لها رأسه، وهي في حجرتها، فترجله وهي حائض.

`Urwah (may Allah be pleased with him) narrated: A person asked me: "Can a woman in menses serve me? And can a Junub [in the state of major ritual impurity] woman come close to me?" I replied: "All this is easy for me. All of them can serve me, and there is no harm for any other person to do the same. `A'ishah told me that she used to comb the hair of Allah’s Messenger (peace be upon him) while she was in her menses, and he was in I‘tikaf (in the mosque). He would bring his head near her in her room and she would comb his hair, while she used to be in her menses."