Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 114
Narated By Zirr b. Hubaish : Zirr b. Hubaish said that he heard that 'Ali was asked how the Apostle of Allah (pbuh) used to perform ablution. He then narrated the tradition and said: He wiped his head so much that drops (of water) were about to trickle down. He then washed his feet three times and said: "This is how the Apostle of Allah (pbuh) performed ablution.