Sunan An-Nasai, Chapter: The Book of Purification

"I saw Uthman bin Affan, may Allah be pleased with him, performing Wudu. He poured water on his hands three times and washed them, then he rinsed his mouth and his nose, then he washed his face three times, then he washed right arm to the elbow three times, then the left likewise. Then he wiped his head, then he washed his right foot three times, then the left likewise. Then he said: 'I saw the Messenger of Allah (saw) performing Wudu like I have just done. Then he said: 'Whoever performs Wudu as I have done, then prays two Rak'ahs without letting his thoughts wander, his previous sins will be forgiven.'" (Sahih)