Ma'bad al-Juhani (may Allah have mercy on him) said: Mu'awiyah (may Allah be pleased with him) very seldom narrated hadith from the Messenger of Allah (peace and blessings be upon him); he said in his sermon: I heard the Messenger of Allah (peace and blessings be upon him) say: "Beware of praising one another (flattery), for it is slaughter."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16866