Musnad Ahmad 30:950

Hashim narrated to us, Layth narrated to us, Yazid ibn Abi Habib narrated to me, from 'Arak, from Abu Hurairah, that he heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Indeed, the worst of people is the two-faced one, who comes to these with one face and to those with one face."