The Prophet ﷺ said, "It does not befit a two-faced person to be trustworthy."
حدثنا الخزاعي قال أخبرنا ابن بلال عن ابن عجلان عن عبيد الله بن سلمان الأغر عن أبيه
أن النبي ﷺ قال ما ينبغي لذي الوجهين أن يكون أمينا
Its isnad is sahih, and the Messenger of Allah ﷺ made clear the reality of the two-faced person and his standing when he 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 another face." Agreed upon.