Musnad Ahmad 3:74

Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami narrated to me, Hammad ibn Zayd narrated to us, from al-Hajjaj, from ‘Ata’, from ‘Uthman, who said: I saw the Messenger of Allah (peace and blessings of Allah be upon him) perform ablution. He washed his face three times, and his hands three times, and wiped his head, and washed his feet, washing them.