Musnad Abu Ya'la al-Mawsili 210:29

Zuhayr narrated to us, Mu'alla ibn Mansur narrated to us, Ibn Abi Za'idah narrated to us, Abu Ayyub al-Afriqi narrated to us, from 'Asim, from al-Musayyab ibn Rafi' and Ma'bad, from Harithah ibn Wahb, who said: Hafsah, the wife of the Prophet (peace and blessings of Allah be upon him), narrated to me that the Messenger of Allah (peace and blessings of Allah be upon him) used to use his right hand for his food and his drink, and he used to use his left hand for what was other than that.