وَإِن طَائِفَتَانِ مِنَ الْمُؤْمِنِينَ اقْتَتَلُوا فَأَصْلِحُوا بَيْنَهُمَا ...

How should Muslims live and behave with each other? The short answer to this question is that they should live with each other as brothers. A religious relationship is in no way less important than a blood relationship. If two Muslims quarrel with each other, other Muslims should never add fuel to the fire. On the contrary, under the influence of brotherly feelings, they should make every effort to bring about a compromise between the two. If two Muslims quarrel with each other, one alternative is for other Muslims to adopt a neutral posture. If they do intervene, or their family or group cause them to take the side of their ‘own’ people and fight against the other ‘alien’ people, either course is contrary to Islamic principles. The right Islamic way is to investigate the real issue, and the one who is right should be supported and the one in the wrong should be compelled to accept a just solution to the problem. One who fears God can never relish the sight of people fighting with each other. In fact, he will be extremely uneasy at such a sight, and his true nature will compel him to make efforts to improve relations between the two parties. These are the people whose faith in God causes the opening of the door to God’s graces.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (49:9)