It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Help your brother, whether he is a wrongdoer or wronged." It was asked: O Messenger of Allah, I will help the one who is wronged, but how shall I help the wrongdoer? He (peace and blessings be upon him) said: "Restraining him from wrongdoing; that is your help to him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الغصب / 11509