Musannaf Ibn Abi Shayba 1:806

806. Khalid ibn Hayyan narrated to us, from Ja'far ibn Burqan, from 'Ikrimah, that he was asked about a woman performing ghusl (ritual bath) for janabah (major ritual impurity) and menstruation. He said: "She should loosen her braids and pour water over her head until she wets the roots of the hair, and she does not need to undo her hair."