Musannaf Ibn Abi Shayba 1:62

Waki’ narrated to us, from Sufyan, from Abu al-Nadr, from Ibn Anas, that Uthman performed ablution at al-Maqa’id. He said, "Shall I not show you the ablution of the Messenger of Allah, may Allah bless him and grant him peace?" Then he performed ablution three times [for each part].