Musnad Abu Ya'la al-Mawsili 159:17

Abu Khaythama narrated to us, Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him), who said: "You will find the worst of people to be the two-faced one, who comes to these with one face and to those with one face."