Musnad Ahmad 1007:49

Abu al-Mughirah narrated to us, al-Awza'i narrated to us, Ibn Abi Kathir narrated to me, from Abdullah ibn Abi Qatadah al-Ansari, my father narrated to me that: He heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "When one of you urinates, let him not touch his private part with his right hand, and let him not clean himself (istinja) with his right hand, and let him not breathe into the vessel."