Helping the oppressor and the oppressed

عَنْ أَنَسٍ ـ رضى اللّٰهُ عنه ـ قَالَ قَالَ رَسُولُ اللّٰه صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم ‏”انْصُرْ أَخَاكَ ظَالِمًا أَوْ مَظْلُومًا”‏‏.‏ قَالُوا يَا رَسُولَ اللّٰه هَذَا نَنْصُرُهُ مَظْلُومًا، فَكَيْفَ نَنْصُرُهُ ظَالِمًا قَالَ ‏”‏تَأْخُذُ فَوْقَ يَدَيْهِ‏”‏‏.‏

Hazrat Anas^ra narrated, “Allah’s Messenger^sa said, ‘Help your brother be he the oppressor or the oppressed.’ The companions said, ‘O Allah’s Messenger^sa, we understand that we should help him when he is the aggrieved party, but how should we help him when he is the wrongdoer?’ He said: ‘Hold his hand [i.e., stop him from oppressing.]’”

(Sahih al-Bukhari, Kitab al-mazalim, Bab a‘in akhaka zaliman aw mazluman, Hadith 2444)