Sunan Abi Dawud, Hadith 4892

Anas b. Malik reported the Messenger of Allah (May peace be upon him) as saying: Do not hate each other; do not envy each other; do not desert each other; and be the servants of Allah as brethren. It is not allowed for a Muslim to keep apart from his brother for more than three days.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ تَبَاغَضُوا وَلاَ تَحَاسَدُوا وَلاَ تَدَابَرُوا وَكُونُوا عِبَادَ اللَّهِ إِخْوَانًا وَلاَ يَحِلُّ لِمُسْلِمٍ أَنْ يَهْجُرَ أَخَاهُ فَوْقَ ثَلاَثِ لَيَالٍ ‏" ‏ ‏.‏

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also referenced under: Hadith 4910 (DarusSalam)