Musnad Abu Ya'la al-Mawsili 210:11

Abdullah bin Amir bin Zurarah al-Kufi narrated to us, Ibn Abi Za'idah narrated to us, from Abu Ayyub, from Asim, from al-Musayyab bin Rafi' and Ma'bad, from Harithah bin Wahb al-Khuza'i, who said: Hafsa, the wife of the Prophet, may Allah bless him and grant him peace, narrated to me that the Messenger of Allah, may Allah bless him and grant him peace, used to use his right hand for his food, and he used to use his left hand for what was other than that.