“Help your brother whether he is an oppressor or oppressed!”

A man said:

“O Allah’s Messenger, I will help him if he is oppressed, but if he is an oppressor, how shall I help him?”

The Prophet صلى الله عليه وآله وسلم said:

“By preventing him from oppressing – that is how to help him.”

[narrated in Ṣaḥīḥ al-Bukhārī]