Sayyiduna Anas bin Malik, may Allah be pleased with him, narrates this statement of the Prophet Muhammad, peace and blessings be upon him: "Help your brother whether he is an oppressor or oppressed." The people asked: "O Messenger of Allah! We will help the oppressed, but how should we help the oppressor?" The Prophet Muhammad, peace and blessings be upon him, said: "By preventing him from oppression."
Hadith Referenceصحیح ابن حبان / كتاب الغصب / 5168
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - المصدر نفسه.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح رجال ثقات رجال الشيخين