It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) in a marfu’ form that you cannot enter Paradise until you become a complete believer, and you cannot become complete until you love one another. Shall I not tell you the root of these things? Spread salam (greetings of peace) among yourselves.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 9084
Hadith Gradingحکم دارالسلام:حديث صحيح، م: 54، وهذا إسناد فيه شريك، وقد توبع