English Translation
Narrated Anas: Allah's Apostle said, "Help your brother, whether he is an oppressor or he is an oppressed one. People asked, "O Allah's Apostle! It is all right to help him if he is oppressed, but how should we help him if he is an oppressor?" The Prophet said, "By preventing him from oppressing others."
This hadith is from Sahih al-Bukhari, the most rigorously authenticated collection in Islamic scholarship. No editorial opinion is added.