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.'"
English reference: Vol. 1, Book 1, Hadith 311
Arabic reference: Book 1, Hadith 332