because to take pleasure in another's evil belongs to hatred, which is contrary to the charity whereby we are bound to love all men.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil pleasure
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

“Accordingly, in the matter of vengeance, we must consider the mind of the avenger. For if his intention is directed chiefly to the evil of the person on whom he takes vengeance and rests there, then his vengeance is altogether unlawful: because to take pleasure in another's evil belongs to hatred, which is contrary to the charity whereby we are bound to love all men. 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” source