Musnad Ahmad 3:95

Sufyan ibn 'Uyaynah narrated to us, from Hisham, from his father, from Humran, the freed slave of 'Uthman: That 'Uthman performed ablution (wudu) at the seats (al-maqā'id), and he washed [each part] three times, three times. And he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Whoever performs ablution like this ablution of mine, then stands for prayer, his sins fall away," meaning from his face, his hands, his feet, and his head.