Council of Trent: Session VI, Justification, Chapter VIII

CHAPTER VIII. In what manner it is to be understood, that the impious is justified by faith, and gratuitously.

And whereas the Apostle saith, that man is justified by faith and freely, those words are to be understood in that sense which the perpetual consent of the Catholic Church hath held and expressed; to wit, that we are therefore said to be justified by faith, because faith is the beginning of human salvation, the foundation, and the root of all Justification; without which it is impossible to please God, and to come unto the fellowship of His sons: but we are therefore said to be justified freely, because that none of those things which precede justification-whether faith or works-merit the grace itself of justification. For, if it be a grace, it is not now by works, otherwise, as the same Apostle says, grace is no more grace.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).