Be not overcome by evil, but overcome evil by good.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil overcoming
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Nor is it an excuse that he intends the evil of one who has unjustly inflicted evil on him, as neither is a man excused for hating one that hates him: for a man may not sin against another just because the latter has already sinned against him, since this is to be overcome by evil, which was forbidden by the Apostle, who says (Rom. 12:21) : "Be not overcome by evil, but overcome evil by good." If, however, the avenger's intention be directed chiefly to some good, to be obtained by means of the punishment of the person who has sinned (for instance that the sinner may amend, or at least that he may be restrained and others be not disturbed, that justice may be upheld, and God honored)” source