Musnad Ahmad #396

It was narrated that Humran bin Aban said: I saw `Uthman bin `Affan (رضي الله عنه) do wudoo`, He poured water onto his hands three times and washed them, then he rinsed his mouth and nose, then he washed his face three times, then he washed his right arm up to the elbow three times, then the left arm likewise, then he wiped his head, then he washed his right foot three times, then the left foot likewise. He said: I saw the Messenger of Allah (ﷺ) do wudoo` similar to what I just did, then he said: “Whoever does wudoo` as I just did, then prays two rak’ahs without letting his mind wander, his previous sins will be forgiven”