Musnad Ahmad 33:2

'Abd al-Malik ibn 'Amr narrated to us, Hisham—meaning Ibn Sa'd—narrated to us, from Zayd ibn Aslam, from 'Ubayd Allah ibn Miqsam, who said: Al-Hasan ibn Muhammad asked Jabir ibn 'Abd Allah about the ritual bath (ghusl) for major ritual impurity (janabah). He said: "You moisten the hair and wash the skin." He said: "How did the Messenger of Allah, peace and blessings of Allah be upon him, perform the ritual bath?" He said: "He used to pour [water] over his head three times." He said: "My head has a lot of hair." He said: "The head of the Messenger of Allah, peace and blessings of Allah be upon him, had more hair than yours, and was better."