Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 116
Narated By Abu Hayyah : I saw 'Ali perform ablution. He (Abu Hayyah) then described that 'Ali went through every part of the ablution three times, i.e. he performed each detail of his ablution three times. He then wiped his head, then washed his feet up to the ankles. He then said: I wanted to show you how the Apostle of Allah (pbuh) performed ablution.