Musnad Ahmad 3:91

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Muhammad ibn Ibrahim ibn al-Harith al-Taymi narrated to me, from Mu'adh ibn 'Abd al-Rahman al-Taymi, from Humran ibn Aban, the freed slave of 'Uthman ibn 'Affan, who said: I saw 'Uthman ibn 'Affan call for water for ablution while he was at the door of the mosque. He washed his hands, then rinsed his mouth, inhaled water into his nose, and blew it out. Then he washed his face three times, then washed his hands up to the elbows three times, then wiped his head, and passed his hands over the outer parts of his ears, then passed them over his beard, then washed his feet up to the ankles three times. Then he stood up and performed two rak'ahs, then said: "I have performed ablution for you just as I saw the Messenger of Allah (peace and blessings of Allah be upon him) perform ablution, then I performed two rak'ahs just as I saw him perform them." He said: Then he said, the Messenger of Allah (peace and blessings of Allah be upon him) said when he finished his two rak'ahs: "Whoever performs ablution as I have performed this ablution, then performs two rak'ahs in which he does not speak to himself (about worldly matters), his sins between that and his prayer of yesterday will be forgiven."