Narrated Ammar: The Prophet (peace_be_upon_him) said:

He who is Two-Faced in this world will have Two Tongues of fire on the Day of Resurrection. ( Sunan Abu Dawud Book 41, Number 4855)

Narrated by Abu Hurairah; he said: Allah's Messenger (peace be upon him) said,

"The worst of all people is the double-faced one, who comes to some people with one face and to others, with another face." [Bukhari, Book 89, Hadith 290]