عَنْ أَنَسٍ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ ((انْصُرْ أَخَاكَ ظَالِمًا أَوْ مَظْلُومًا)) قِيلَ يَا رَسُولَ اللَّهِ هَذَا نَنْصُرُهُ مَظْلُومًا فَكَيْفَ نَنْصُرُهُ ظَالِمًا قَالَ ((تَمْنَعُهُ مِنَ الظُّلْمِ)) وَفِي لَفْظٍ ((تَحْجِزُهُ تَمْنَعُهُ مِنَ الظُّلْمِ فَإِنَّ ذَلِكَ نَصْرُهُ))
It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Help your brother, whether he is an oppressor or oppressed. Someone asked: O Messenger of Allah! I understand that we should help the oppressed, but how can we help the oppressor? The Prophet (peace and blessings be upon him) said: Prevent him from oppression. In another narration it is stated: Stop him from oppression; this, in fact, will be his help.