"Help your brother whether he is an oppressor or oppressed." It was said: "O Messenger of Allah! I help him when he is oppressed. But how can I help him when he oppresses?" He said: "Prevent him from oppression, that is your help for him."  

عَنِ النَّبِيِّ ﷺ قَالَ انْصُرْ أَخَاكَ ظَالِمًا أَوْ مَظْلُومًا قُلْنَا يَا رَسُولَ اللَّهِ نَصَرْتُهُ مَظْلُومًا فَكَيْفَ أَنْصُرُهُ ظَالِمًا قَالَ تَكُفُّهُ عَنِ الظُّلْمِ فَذَاكَ نَصْرُكَ إِيَّاهُ قَالَ وَفِي الْبَابِ عَنْ عَائِشَةَ