Sahih Muslim Book - 45, Hadith - 6582

حَدَّثَنَا أَحْمَدُ بْنُ عَبْدِ اللهِ بْنِ يُونُسَ ، حَدَّثَنَا زُهَيْرٌ ، حَدَّثَنَا أَبُو الزُّبَيْرِ ، عَنْ جَابِرٍ ، قَالَ : اقْتَتَلَ غُلاَمَانِ غُلاَمٌ مِنَ الْمُهَاجِرِينَ ، وَغُلاَمٌ مِنَ الأَنْصَارِ ، فَنَادَى الْمُهَاجِرُ أَوِ الْمُهَاجِرُونَ ، يَا لَلْمُهَاجِرِينَ وَنَادَى الأَنْصَارِيُّ يَا لَلأَنْصَارِ ، فَخَرَجَ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، فَقَالَ: مَا هَذَا دَعْوَى أَهْلِ الْجَاهِلِيَّةِ قَالُوا : لاَ يَا رَسُولَ اللهِ ، إِلاَّ أَنَّ غُلاَمَيْنِ اقْتَتَلاَ فَكَسَعَ أَحَدُهُمَا الآخَرَ ، قَالَ: فَلاَ بَأْسَ وَلْيَنْصُرِ الرَّجُلُ أَخَاهُ ظَالِمًا ، أَوْ مَظْلُومًا ، إِنْ كَانَ ظَالِمًا فَلْيَنْهَهُ ، فَإِنَّهُ لَهُ نَصْرٌ وَإِنْ كَانَ مَظْلُومًا فَلْيَنْصُرْهُ.

It was narrated that Jabir said: "Two young men got into a fight, one from among the Muhajirin and one from among the Ansar. The Muhajir or the Muhajirin called out: 'O Muhajirin!' And the Ansari called out: 'O Ansar!' The Messenger of Allah (s.a.w) came out and said: 'What is this call of the people of Jahiliyyah?' They said: No, O Messenger of Allah. It is just two young men who got into a fight, when one of them hit the other from behind.' He said: 'It does not matter. Let a man support his brother whether he is doing wrong or being wronged. If he is doing wrong, let him stop him, then he will be supporting him. And if he is being wronged, let him help him."'