Musnad Ahmad 1007:139

Muhammad ibn Abi ‘Adi narrated to us, from al-Hajjaj ibn Abi ‘Uthman al-Sawwaf, from Yahya ibn Abi Kathir, from ‘Abdullah ibn Abi Qatadah, from his father, that the Messenger of Allah (may Allah bless him and grant him peace) said: "When one of you drinks, let him not breathe into the vessel. And when he enters the privy, let him not cleanse himself with his right hand. And when he urinates, let him not touch his private part with his right hand."