Sahih Muslim Book 3, Hadith Number 646.
Chapter : Law of Shari’ah pertaining to the plaited hair of the woman who takes a bath.
‘Ubaid b. Umair reported: It was conveyed to ‘Aisha that ‘Abdullah b. ‘Amr ordered the women to undo the (plaits) of hair on their heads. She said: How strange it is for Ibn ‘Amr that he orders the women to undo the plates of their head while taking a bath; why does he not order them to shave their beads? I and the Messenger of Allah (may peace be upon him) took bath from one vessel. I did no more than this that I poured three handfuls of water over my head.