Musnad Ahmad 27:1065

Muhammad ibn Ubayd narrated to us, Ubayd Allah ibn Umar narrated to us, from Nafi, from Ibn Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Let not one of you eat with his left hand, and let him not drink with his left hand, for indeed, the Shaytan eats with his left hand and drinks with his left hand."