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.