The Messenger of Allah ﷺ said, "By the One in whose hand my soul rests, you will not enter Paradise until you believe, and you will not truly believe until you love one another. Shall I guide you to something which, if you do it, will make you love one another? Spread the greeting of peace among yourselves."
حدثنا هناد حدثنا أبو معاوية عن الأعمش عن أبي صالح
قال رسول الله ﷺ والذي نفسي بيده لا تدخلوا الجنة حتى تؤمنوا ولا تؤمنوا حتى تحابوا ألا أدلكم على أمر إذا أنتم فعلتموه تحاببتم أفشوا السلام بينكم
Muslim also narrated it in the Book of Faith, chapter on the statement that only believers enter Paradise, etc., hadith 54, from the hadith of Abu Muawiya al-Darir, with this same chain.On this topic, there are also narrations from Abdullah bin Salam [mentioned previously at 2485], Shurayh bin Hani from his father [Bukhari in Adab al-Mufrad, hadith 811], Abdullah bin Amr [mentioned previously at 1855], Bara [coming up at 2726], Anas [Bayhaqi in Shuab al-Iman, hadith 3367], and Ibn Umar [Ibn Majah, hadith 3252].