Musnad Ahmad 790:128

'Abd al-Samad narrated to us, Hajib ibn 'Umar narrated to us, al-Hakam ibn al-A'raj narrated to us, that 'Imran ibn Husayn said: "I have not touched my private part with my right hand since I pledged allegiance to the Messenger of Allah, may Allah bless him and grant him peace, with it."