Hadith 8
Al-Zubayr ibn ‘Awwam reported: The Messenger of Allah, peace and blessings be upon him, said:
دَبَّ إِلَيْكُمْ دَاءُ الْأُمَمِ قَبْلَكُمْ الْحَسَدُ وَالْبَغْضَاءُ وَالْبَغْضَاءُ هِيَ الْحَالِقَةُ حَالِقَةُ الدِّينِ لَا حَالِقَةُ الشَّعَرِ وَالَّذِي نَفْسُ مُحَمَّدٍ بِيَدِهِ لَا تُؤْمِنُوا حَتَّى تَحَابُّوا أَفَلَا أُنَبِّئُكُمْ بِشَيْءٍ إِذَا فَعَلْتُمُوهُ تَحَابَبْتُمْ أَفْشُوا السَّلَامَ بَيْنَكُمْ
Lurking towards you are the diseases of the nations before you. Envy and hatred are the razor. I do not say they shave hair, but rather they shave the religion. By the One in whose hand is my soul, you will not enter Paradise until you have faith and you will not have faith until you love each other. Shall I tell you what can affirm that for you? Spread peace between yourselves.
Source: Sunan al-Tirmidhī 2510, Grade: Sahih