for man's sins are not forgiven through his own merits
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic sin merit
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/19950/pg19950-images.html

Context

“It would seem that infusion of grace is necessary for the remission of venial sins. Because an effect is not produced without its proper cause. Now the proper cause of the remission of sins is grace; for man's sins are not forgiven through his own merits; wherefore it is written (Eph. 2:4, 5) : "God, Who is rich in mercy, for His exceeding charity, wherewith He loved us, even when we were dead in sins, hath quickened us together in Christ, by Whose grace you are saved."” source