Sunan Ibn Majah — The Book of Purification and its Sunnah — Hadith No: 311
Translation
It was narrated that 'Uqbah bin Suhban said:"I heard 'Uthman bin 'Affan say: 'I never sang a song or told a lie or touched my penis with my right hand after I swore on oath of allegiance to the Messenger of Allah to that effect