Abu Dawud Book 1, Hadith Number 137.
Chapter : Washing the limbs in ablution twice.
Narated By ‘Ata b. Yasar quoting Ibn ‘Abbas : Do you like that I should show you how the Messenger (peace be upon him) performed ablution? He then called for a vessel of water and took a handful of water with his right hand. He then rinsed his mouth and snuffed up water. He then took out another handful of water and washed his face by both his hands together. He then took out another handful of water and washed his right hand and then washed his left hand by taking out another. He then took out some water and shook his hand and wiped his head and ears with it. He then took out a handful of water and sprinkled it over his right foot in his shoe and wiped the upper part of the foot with one hand, and beneath the shoe with his other hand. He then did the same with his left foot.