Now, they [the adults] are disposed to that justice when, aroused and aided by divine grace, receiving faith by hearing,[21] they are moved freely toward God, believing to be true what has been divinely revealed and promised, especially that the sinner is justified by God by his grace, through the redemption that is in Christ Jesus;[22] and when, understanding themselves to be sinners, they, by turning themselves from the fear of divine justice, by which they are salutarily aroused, to consider the mercy of God, are raised to hope, trusting that God will be propitious to them for Christ’s sake; and they begin to love Him as the fountain of all justice, and on that account are moved against sin by a certain hatred and detestation, that is, by that repentance that must be performed before baptism;[23] finally, when they resolve to receive baptism, to begin a new life and to keep the commandments of God.
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 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.