You will not enter Paradise until you believe, and you will not truly believe until you love one another. Shall I guide you to the foundation of that, or to what holds it together? Spread the greeting of peace among yourselves.Sharik sometimes said, "Shall I guide you to something which, if you do it, will cause you to love one another? Spread the greeting of peace among yourselves."
حدثنا أسود حدثنا شريك عن الأعمش عن أبي صالح
لا تدخلون الجنة حتى تؤمنوا ولا تؤمنون حتى تحابوا ألا أدلكم على رأس ذلك أو ملاك ذلك أفشوا السلام بينكم وربما قال شريك ألا أدلكم على شيء إذا فعلتموه تحاببتم أفشوا السلام بينكم
Its chain of transmission is sahih. Muslim narrated it, 1/74, no. 54, in the Book of Faith, chapter on the explanation that only believers enter Paradise. Abu Dawud narrated it, 4/350, no. 5193, in the Book of Manners, chapter on spreading greetings of peace, and he said, hasan sahih. Ibn Majah narrated it, 2/1217, no. 3692, in the Book of Manners, chapter on spreading greetings of peace. Bukhari narrated it in Adab al-Mufrad, 330, no. 983.