Musannaf Ibn Abi Shayba 1:138

'Abd al-Rahim ibn Sulayman narrated to us, from Yazid ibn Abi Ziyad, who said: I entered upon 'Abd al-Rahman ibn Abi Layla, and he called for water for ablution. He performed ablution, wiped his head once, and washed his feet three times by three times. He said: "This is how I saw 'Ali perform ablution."