Musnad Ahmad 5:310

Marwan ibn Mu'awiyah al-Fazari narrated to us, Rabi'ah ibn 'Utbah al-Kinani narrated to us, from al-Minhal ibn 'Amr, from Zirr ibn Hubaysh, who said: "He wiped his head during wudu until it was about to drip, and he said: 'This is how I saw the Messenger of Allah, may Allah bless him and grant him peace, perform wudu.'"