The Prophet ﷺ said, "The disease of the nations before you has crept toward you, envy and hatred. It is the shaver. I do not say it shaves hair, but it shaves religion. By the One in whose hand my soul is, you will not enter Paradise until you believe, and you will not believe until you love one another. Shall I not tell you of something that, if you do it, will establish that love among you? Spread the greeting of peace among yourselves."
حدثنا سفيان بن وكيع حدثنا عبد الرحمن بن مهدي عن حرب بن شداد عن يحيى بن أبي كثير عن يعيش بن الوليد أن مولى الزبير حدثه أن
أن النبي ﷺ قال دب إليكم داء الأمم قبلكم الحسد والبغضاء هي الحالقة لا أقول تحلق الشعر ولكن تحلق الدين والذي نفسي بيده لا تدخلوا الجنة حتى تؤمنوا ولا تؤمنوا حتى تحابوا أفلا أنبئكم بما يثبت ذاكم لكم أفشوا السلام بينكم
[Its isnad is daif] Ahmad narrated it in 2/167 from Ibn Mahdi through the same route. The freedman of Zubayr, I did not find anyone who deemed him trustworthy, and part of the hadith has corroborating narrations. There is also another discrepancy in the chain as found in Bazzar.