Hadith 4631
وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَدْخُلُونَ الْجَنَّةَ حَتَّى تُؤْمِنُوا وَلَا تُؤْمِنُوا حَتَّى تَحَابُّوا أَو لَا أدلكم على شَيْء إِذا فعلمتموه تحاببتم؟ أفشوا السَّلَام بَيْنكُم» رَوَاهُ مُسلم
Abu Huraira (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "You cannot enter Paradise until you become believers, and you cannot become believers until you love one another. Shall I not tell you about something which, if you do it, you will love one another? Spread peace among yourselves." Narrated by Muslim.