It was narrated that Abu Hurairah said: "The Messenger of Allah (ﷺ) said: “By the One in whose Hand is my soul! You will not enter Paradise until you believe, and you will not (truly) believe until you love one another. Shall I not tell you of something which, if you do it, you will love one another? Spread the greetings of Salam amongst yourselves”"
SahihSahihSahihBook 0 · Hadith 68