وَإِن طَائِفَتَانِ مِنَ الْمُؤْمِنِينَ اقْتَتَلُوا فَأَصْلِحُوا بَيْنَهُمَا فَإِن بَغَتْ إِحْدَاهُمَا عَلَى الْأُخْرَى فَقَاتِلُوا الَّتِي تَبْغِي حَتَّى تَفِيءَ إِلَى أَمْرِ اللَّهِ فَإِن فَاءتْ فَأَصْلِحُوا بَيْنَهُمَا بِالْعَدْلِ وَأَقْسِطُوا إِنَّ اللَّهَ يُحِبُّ الْمُقْسِطِينَ
﴿٩﴾
سورة الحُـجُـرات
(49/9) And if two groups of the believers fight, make peace between them. But if one of them attacks the other, then fight against the group that attacked till they return to the Command of Allah. Then if they return, then make peace between them, be just (to them and do not tyrannize the other). Surely Allah loves those who act justly.
Surah Al-Hujurat