Council of Trent: Session 6
Chapter 8
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.
Chapter 9
Against the vain confidence of Heretics.
But, although it is necessary to believe that sins neither are remitted, nor ever were remitted save gratuitously by the mercy of God for Christ's sake; yet is it not to be said, that sins are forgiven, or have been forgiven, to any one who boasts of his confidence and certainty of the remission of his sins, and rests on that alone; seeing that it may exist, yea does in our day exist, amongst heretics and schismatics; and with great vehemence is this vain confidence, and one alien from all godliness, preached up in opposition to the Catholic Church. But neither is this to be asserted,—that they who are truly justified must needs, without any doubting whatever, settle within themselves that they are justified, and that no one is absolved from sins and justified, but he that believes for certain that he is absolved and justified; and that absolution and justification are effected by this faith alone: as though whoso has not this belief, doubts of the promises of God, and of the efficacy of the death and resurrection of Christ. For even as no pious person ought to doubt of the mercy of God, of the merit of Christ, and of the virtue and efficacy of the sacraments, even so each one, when he regards himself, and his own weakness and indisposition, may have fear and apprehension touching his own grace; seeing that no one can know with a certainty of faith, which cannot be subject to error, that he has obtained the grace of God.
Chapter 10
On the increase of Justification received.
Having, therefore, been thus justified, and made the friends and domestics of God, advancing from virtue to virtue, they are renewed, as the Apostle says, day by day; that is, by mortifying the members of their own flesh, and by presenting them as instruments of justice unto sanctification, they, through the observance of the commandments of God and of the Church, faith co-operating with good works, increase in that justice which they have received through the grace of Christ, and are still further justified, as it is written; He that is just, let him be justified still; and again, Be not afraid to be justified even to death; and also, Do you see that by works a man is justified, and not by faith only. And this increase of justification holy Church begs, when she prays, "Give unto us, O Lord, increase of faith, hope, and charity."