BELIEVE in God and His Apostle, and spend on others out of that of which He has made you trustees: or, those of you who have attained to faith and who spend freely [in God’s cause] shall have a great reward.
Al-Hadid (Iron) Verse 7
Allah's Apostle said, "Help your brother, whether he is an oppressor or he is an oppressed one. People asked, "O Allah's Apostle! It is all right to help him if he is oppressed, but how should we help him if he is an oppressor?" The Prophet said, "By preventing him from oppressing others."
Sahih Bukhari: Volume 3, Book 43, Number 624