Hadith: "Support your brother whether he is an oppressor or oppressed."* A man said: O Messenger of Allah, I support him if he is oppressed, but how should I support him if he is an oppressor? He said: "Stop—or prevent—him from oppression. This is indeed supporting him."

عَنْ أَنَسِ بْنِ مَالِكٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ:
«انْصُرْ أَخَاكَ ظَالِمًا أَوْ مَظْلُومًا». فَقَالَ رَجُلٌ: يَا رَسُولَ اللَّهِ، أَنْصُرُهُ إِذَا كَانَ مَظْلُومًا، أَفَرَأَيْتَ إِذَا كَانَ ظَالِمًا كَيْفَ أَنْصُرُهُ؟ قَالَ: « تَحْجُزُهُ -أَوْ تَمْنَعُهُ- مِنَ الظُّلْمِ؛ فَإِنَّ ذَلِكَ نَصْرُهُ».
[صحيح] - [رواه البخاري] - [صحيح البخاري: 6952]

Anas ibn Mālik (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) said:
"Support your brother whether he is an oppressor or oppressed." A man said: O Messenger of Allah, I support him if he is oppressed, but how should I support him if he is an oppressor? He said: "Stop—or prevent—him from oppression. This is indeed supporting him."
[Authentic hadith] - [Narrated by Bukhari] - [Sahih Bukhari - 6952]

Explanation

The Prophet (may Allah's peace and blessings be upon him) commanded the Muslim to support his fellow Muslim, whether he is an oppressor or oppressed. A man then said: O Messenger of Allah, I support him if he is oppressed by removing the injustice from him, but what if he is the oppressor? How can I support him then? He said: Stop him, restrain him, and prevent him from committing injustice, for it is indeed supporting him against his devil and his own soul that commands evil.

Benefits from the Hadith

1. A reminder of one of the rights of faith-based brotherhood among Muslims.
2. Restraining the oppressor and preventing him from committing injustice.
3. Islam stands in opposition to the concepts of the pre-Islamic era, where people would support one another whether they were oppressed or oppressors.