Anas (R.A) reported: Messenger of Allah (peace be upon him) said, “Help your brother, whether he is an oppressor or is oppressed”. A man enquired: “O Messenger of Allah (peace be upon him)! I help him when he is oppressed, but how can I help him when he is an oppressor?” He (peace be upon him) said, “You can keep him from committing oppression. That will be your help to him”.
Click to read Yesterday and previous days of Islamic Daily Hadith Here
Riyad as-Salihin, Book 1, Hadith 237