Sunan An-Nasai, Chapter: The Book of Purification

that he saw Uthman call for (water for) Wudu, then he poured water on his hands from the vessel and washed them three times. Then he put his right hand in the water and rinsed his mouth and his nose. Then he washed his face three times, and his arms up to the elbow three times. Then he wiped his head, and washed each of his feet three times. 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 stands and prays two Rakahs without letting his thoughts wander, his previous sins will be forgiven.'" (Sahih)