The point being made here is that justification is by faith alone,
americancatholictruthsociety.com/docs/TRENT/trent6.htm
CHAPTER III
WHO ARE JUSTIFIED THROUGH CHRIST
But though He died for all,[16] yet all do not receive the benefit of His death, but those only to whom the merit of His passion is communicated; because as truly as men would not be born unjust, if they were not born through propagation of the seed of Adam, since by that propagation they contract through him, when they are conceived, injustice as their own, so if they were not born again in Christ, they would never be justified, since in that new birth there is bestowed upon them, through the merit of His passion, the grace by which they are made just.
For this benefit the Apostle exhorts us always to give thanks to the Father, who hath made us worthy to be partakers of the lot of the saints in light, and hath delivered us from the power of darkness, and hath translated us into the kingdom of the Son of his love, in whom we have redemption and remission of sins.[17]
CHAPTER VII
IN WHAT THE JUSTIFICATION OF THE SINNER CONSISTS, AND WHAT ARE ITS CAUSES
This disposition or preparation is followed by justification itself, which is not only a remission of sins but also the sanctification and renewal of the inward man through the voluntary reception of the grace and gifts whereby an unjust man becomes just and from being an enemy becomes a friend, that he may be an heir according to hope of life everlasting.[30]
The causes of this justification are:
the final cause is the glory of God and of Christ and life everlasting; the efficient cause is the merciful God who washes and sanctifies[31] gratuitously, signing and anointing with the holy Spirit of promise, who is the pledge of our inheritance,[32] the meritorious cause is His most beloved only begotten, our Lord Jesus Christ, who, when we were enemies,[33] for the exceeding charity wherewith he loved us,[34] merited for us justification by His most holy passion on the wood of the cross and made satisfaction for us to God the Father, the instrumental cause is the sacrament of baptism, which is the sacrament of faith,[35] without which no man was ever justified finally, the single formal cause is the justice of God, not that by which He Himself is just, but that by which He makes us just, that, namely, with which we being endowed by Him, are renewed in the spirit of our mind,[36] and not only are we reputed but we are truly called and are just, receiving justice within us, each one according to his own measure, which the Holy Ghost distributes to everyone as He wills,[37] and according to each one’s disposition and cooperation.
For though no one can be just except he to whom the merits of the passion of our Lord Jesus Christ are communicated, yet this takes place in that justification of the sinner, when by the merit of the most holy passion, the charity of God is poured forth by the Holy Ghost in the hearts[38] of those who are justified and inheres in them; whence man through Jesus Christ, in whom he is ingrafted, receives in that justification, together with the remission of sins, all these infused at the same time, namely, faith, hope and charity.
For faith, unless hope and charity be added to it, neither unites man perfectly with Christ nor makes him a living member of His body.[39]
For which reason it is most truly said that faith without works is dead[40] and of no profit, and in Christ Jesus neither circumcision availeth anything nor uncircumcision, but faith that worketh by charity.[41]
This faith, conformably to Apostolic tradition, catechumens ask of the Church before the sacrament of baptism, when they ask for the faith that gives eternal life, which without hope and charity faith cannot give.
Whence also they hear immediately the word of Christ:
If thou wilt enter into life, keep the commandments.[42]
Wherefore, when receiving true and Christian justice, they are commanded, immediately on being born again, to preserve it pure and spotless, as the first robe[43] given them through Christ Jesus in place of that which Adam by his disobedience lost for himself and for us, so that they may bear it before the tribunal of our Lord Jesus Christ and may have life eternal.
CHAPTER IX
AGAINST THE VAIN CONFIDENCE OF HERETICS
But though it is necessary to believe that sins neither are remitted nor ever have been remitted except gratuitously by divine mercy for Christ’s sake, yet it must not be said that sins are forgiven or have been forgiven to anyone who boasts of his confidence and certainty of the remission of his sins,[47] resting on that alone, though among heretics and schismatics this vain and ungodly confidence may be and in our troubled times indeed is found and preached with untiring fury against the Catholic Church.
Moreover, it must not be maintained, that they who are truly justified must needs, without any doubt whatever, convince themselves that they are justified, and that no one is absolved from sins and justified except he that believes with certainty that he is absolved and justified,[48] and that absolution and justification are effected by this faith alone, as if he who does not believe this, doubts the promises of God and the efficacy of the death and resurrection of Christ.
For as no pious person ought to doubt the mercy of God, the merit of Christ and the virtue and efficacy of the sacraments, so each one, when he considers himself and his own weakness and indisposition, may have fear and apprehension concerning his own grace, since no one can know with the certainty of faith, which cannot be subject to error, that he has obtained the grace of God.