Nothing is a sin that the true faith employs in worshipping God.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic sin faith
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

“was used to signify any worship of a creature, even without the use of images. _______________________ SECOND ARTICLE [II-II, Q. 94, Art. 2] Whether Idolatry Is a Sin? Objection 1: It would seem that idolatry is not a sin. Nothing is a sin that the true faith employs in worshipping God. Now the true faith employs images for the divine worship: since both in the Tabernacle were there images of the cherubim, as related in Ex. 25, and in the Church are images set up which the faithful worship.” source