Malik related to me from Abu'z-Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "One of the most evil of people is the two-faced person who shows one face to these people and another face to those people."


وَحَدَّثَنِي مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مِنْ شَرِّ النَّاسِ ذُو الْوَجْهَيْنِ الَّذِي يَأْتِي هَؤُلاَءِ بِوَجْهٍ وَهَؤُلاَءِ بِوَجْهٍ ‏"‏ ‏.‏
USC-MSA web (English) reference : Book 56, Hadith 21
Arabic reference : Book 56, Hadith 1834