Sahih al-Bukhari 1934

Abdan narrated to us: Abdullah informed us: Ma mar narrated to us, saying: al-Zuhri narrated to me, from Ata bin Yazid, from Humran: I saw Uthman, may Allah be pleased with him, perform ablution. He poured water over his hands three times, then rinsed his mouth and expelled water from his nose. Then he washed his face three times, his right arm up to the elbow three times, and his left arm up to the elbow three times. Then he wiped his head, washed his right foot three times, then his left foot three times. He said: I saw the Messenger of Allah, peace and blessings be upon him, perform ablution like this ablution of mine. Then he said: Whoever performs ablution like this, then prays two units without thinking of anything during them, will have his past sins forgiven.