Musnad Abu Ya'la al-Mawsili 4:5

Ghassan ibn al-Rabi' narrated to us, Layth ibn Sa'd narrated to us, from Yazid ibn Abi Habib, from Abu al-Nasr, that 'Uthman ibn 'Affan called for water for ablution, and with him were al-Zubayr, Talhah, 'Ali, and Sa'd. Then he performed ablution while they were looking. He washed his face three times, then poured [water] over his right [hand] three times and washed his left [hand] three times. He wiped his head, then sprinkled [water] on his right foot, then washed it three times. Then he sprinkled [water] on his left foot, then washed it three times. Then he said to those who were present: "I adjure you by Allah, do you know that the Messenger of Allah, peace and blessings of Allah be upon him, used to perform ablution just as I have performed it now?" They said: "Yes." And that was because of something that had reached him regarding the ablution of some people.