Smile in your face and stab you in the back

يبتسمون في وجهك و يطعنونك بظهرك-يعني من يتظاهر بالود والصداقة تجاهك و بمغيبك يذمون و يجرحون شخصك

When someone pretends or portrays themselves as your friend, or that they have your interests, your welfare at heart but instead they are involved in treacherous actions/words against you. Theses actions/words are used to benefit them by discrediting you. They might figuratively be patting you on the back with one hand, and knifing you with the other. You think they are doing good for you and find out that their personal priorities are unscrupulous (corrupt).