Muwatta Malik 98

Yahya related to me from Malik from Hisham ibn Urwa from his father from A'isha, umm al-muminin, that whenever the Messenger of Allah, may Allah bless him and grant him peace, did ghusl for major ritual impurity, he would begin by washing his hands, and then do wudu as for prayer. He would then put his fingers in the water and rub the roots of his hair with them. Then he would pour as much water as two hands can hold on to his head three times, and over the entire surface of his skin