Sahih Bukhari

Narrated Anas:Allah's Messenger (ﷺ) said, ""Help your brother whether he is an oppressor or an oppressed,"" A man said, ""O Allah's Messenger (ﷺ)! I will help him if he is oppressed, but if he is an oppressor, how shall I help him?"" The Prophet (ﷺ) said, ""By preventing him from oppressing (others), for that is how to help him