You become worse than the sinner if you fail to correct him.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic
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

“which appears to be inconvenient, both on account of the great number of sinners, for whose correction one man could not suffice, and because religious would have to leave the cloister in order to reprove men, which would be unbecoming. Therefore fraternal correction is not a matter of precept. On the contrary, Augustine says (De Verb. Dom. xvi, 4) : "You become worse than the sinner if you fail to correct him." But this would not be so unless, by this neglect, one omitted to observe some precept. Therefore fraternal correction is a matter of precept. I answer that, Fraternal correction is a matter of precept.” source