Musnad Ahmad 5:356

'Abdullah narrated to us, Ishaq bin Isma'il narrated to us, Waki' narrated to us, al-Hasan bin 'Uqbah Abu Kabran narrated to us, from 'Abd Khayr, from 'Ali, who said: "This is the ablution of the Messenger of Allah, may Allah bless him and grant him peace." Then he performed ablution three times [for each part].