Musnad Ahmad 3:30

Muhammad ibn Bakr narrated to us, Ibn Jurayj informed us, Ibn Shihab narrated to me, from ‘Ata’ ibn Yazid al-Jundaci, that he heard Humran, the freed slave of ‘Uthman ibn ‘Affan, say: I saw the Commander of the Faithful, ‘Uthman, performing ablution. He poured water over his hands three times, then he blew water from his nose three times and rinsed his mouth three times... and he mentioned the hadith similar to the meaning of the hadith of Ma‘mar.