Council of Trent, Session VI (Jan. 13, 1547)
Decree on Justification,
Chapter IV.
A description is introduced of the Justification of the impious, and of the Manner thereof under the law of grace.
By which words, a description of the Justification of the impious is indicated, as being a translation, from that state wherein man is born a child of the first Adam, to the state of grace, and of the adoption of the sons of God, through the second Adam, Jesus Christ, our Saviour. And this translation, since the promulgation of the Gospel, cannot be effected, without the laver of regeneration, or the desire thereof, as it is written; unless a man be born again of water and the Holy Ghost, he cannot enter into the Kingdom of God.
Catechism from Trent explains OR THE DESIRE THEREOF:Dispositions for baptism
Intention
The faithful are also to be instructed in the necessary dispositions for Baptism. In the first place they must desire and intend to receive it; for as in Baptism we all die to sin and resolve to live a new life, it is fit that it be administered to those only who receive it of their own free will and accord; it is to be forced upon none. Hence
we learn from holy tradition that it has been the invariable practice to administer Baptism to no individual without previously asking him if he be willing to receive it. This disposition even infants are presumed to have, since the will of the Church, which promises for them, cannot be mistaken.
Necessity Of Confession [Doctrine on Perfect Contrition]
Contrition, it is true, blots out sin;
but who does not know that to effect this it must be so intense, so ardent, so vehement, as to bear a proportion to the magnitude of the crimes which it effaces? This is a degree of contrition which few reach; and hence, in this way, very few indeed could hope to obtain the pardon of their sins. It, therefore, became necessary that the most merciful Lord should provide by some easier means for the common salvation of men; and this He has done in His admirable wisdom, by giving to His Church the keys of the kingdom of heaven.
According to the doctrine of the Catholic Church,
a doctrine firmly to be believed and constantly professed by all, if the sinner have a sincere sorrow for his sins and a firm resolution of avoiding them in future, although he bring not with him
that contrition which *may* be sufficient of itself to obtain pardon, all his sins are forgiven and remitted through the power of the keys, when he confesses them properly to the priest. Justly, then, do those most holy men, our Fathers, proclaim that by the keys of the Church the gate of heaven is thrown open, a truth which no one can doubt since the Council of Florence has decreed that the effect of Penance is absolution from sin.