Musnad Ahmad 1153:683

'Affan narrated to us, Hammad ibn Salamah narrated to us, he said: Hisham ibn 'Urwah informed us, from his father, from 'Aishah, "That the Messenger of Allah (peace and blessings of Allah be upon him) used to perform wudu like his wudu for prayer when he wanted to perform ghusl from janabah. Then he would insert his hand into the vessel and trace the roots of his hair. When he thought that he had thoroughly wetted the entire skin, he would pour [water] over his head three times, then he would perform ghusl." And 'Urwah said: Except that he would begin by washing his hand, then his private parts.