Musnad Ahmad 1153:1476

Yazid narrated to us, he said: Hajjaj informed us, from ‘Ata’, from ‘A’ishah, she said: "The Messenger of Allah (peace and blessings of Allah be upon him) would be in a state of major ritual impurity (janabah), then he would sleep. When he awoke, he would perform ghusl (ritual bath) and go out while his head was dripping, then he would fast the remainder of that day."