And you see that the worst among people is the double faced (person) who appears to these with one face and to the others with another face (i.e a hypocrite).
Hadith Referenceصحيح البخاري / كتاب المناقب / 3494
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة