It was narrated that az-Zubair bin al-"Awwam (رضي الله عنه) said:

The Messenger of Allah (ﷺ) said: “There has come to you the disease of the nations before you, jealousy and hatred. Hatred is the "shaver" (destroyer) that shaves (destroys) religious commitment; it does not shave hair. By the One in Whose Hand is the soul of Muhammad, you will not believe until you love one another. Shall I not tell you something which, if you do it, you will love one another? Spread (the greeting of) salam amongst yourselves.”