Sunan An-Nasai, Chapter: The Book of Purification

"I saw Ali call for a chair and he sat down, then he called for water in a vessel and washed his hands three times, then he rinsed his mouth and nose with one hand, three times. Then he washed his face three times, and his hands three times. Then he dipped his hand in the vessel and wiped his head, then he washed each foot three times. Then he said: 'Whoever would like to see how the Messenger of Allah (saw) performed Wudu, this is his Wudu.'" (Sahih)