The Council of Trent
On Justification: Chapter IV: 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 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 the Gospel, can not 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 can not enter into the Kingdom of God.
Canon II: If any one saith, that true and natural water is not of necessity for baptism, and, on that account, wrests, to some sort of metaphor, those words of our Lord Jesus Christ: Unless a man be born again of water and the Holy Ghost: let him be anathema.
Canon V: If any one saith, that baptism is free, that is, not necessary unto salvation: let him be anathema (The Canons and Decrees of the Council of Trent. Found in Philip Schaff, The Creeds of Christendom (New York: Harper, 1877), Decree on Justification, Chapter IV, p. 91; Canons on Baptism II, V; pp. 122-123).
The Code of Canon Law
Canon.849: Baptism, the gateway to the sacraments, is necessary for salvation, either by actual reception or at least by desire. By it people are freed from sins, are born again as children of God and, made like to Christ by an indelible character, are incorporated into the Church. It is validly conferred only by a washing in real water with the proper form of words (The Code of Canon Law (London: Collins, 1983).
The Question and Answer Catholic Catechism
1142. What is baptism?
Baptism is the sacrament of spiritual rebirth. Through the symbolic action of washing with water and the use of appropriate ritual words, the baptized person is cleansed of all his sins and incorporated into Christ. It was foretold in Ezekiel, “I shall pour clean water over you and you will be cleansed; I shall cleanse you of all your defilement and all your idols. I shall give you a new heart, and put a new spirit in you” (Ezekiel 36:25-26).
1151. What are the effects of baptism?
The effects of baptism are the removal of the guilt of sin and all punishment due to sin, conferral of the grace of regeneration and the infused virtues, incorporation into Christ and his Church, receiving the baptismal character and the right to heaven.
1152. What sins does baptism take away?
Baptism remits the guilt of all sins, that is, it takes away all sins, whether original sin as inherited from Adam at conception, or actual sin as incurred by each person on reaching the age of reason. No matter how frequent, or how grave the actual sins may be, their guilt is all removed at baptism. All of this is the pure gift of God, since St. Paul writes, “It was for no reason except his own compassion that he saved us, by means of the cleansing water of rebirth” (Titus 3:5).
1153. What penalties does baptism remove?
Baptism removes all the penalties, eternal and temporal attached to original and actual sin.
1155. What is the grace of regeneration?
The grace of regeneration infuses into our souls the life of grace that Christ won for us by his Death and Resurrection. It is the new birth of which Christ spoke to Nicodemus (cf. John 3:3) and the new creation described by St. Paul (cf. 2 Corinthians 5:17).
1156. What virtues are infused into the soul at baptism?
The virtues infused into the soul at baptism are faith, hope, and charity. Among the gifts of grace infused at baptism are the peace and joy of the Holy Spirit, which make possible the practice of the Beatitudes.
1157. How does baptism incorporate us into Christ?
By baptism we become members of Christ’s Mystical Body, which is the Church. That is why “By the sacrament of baptism, whenever it is properly conferred in the way the Lord determined and received with the proper dispositions of soul, man becomes truly incorporated into the crucified and glorified Christ and is reborn to a sharing of the divine life, as the apostle says: ‘For you were buried together with him in baptism, and in him also rose again through faith in the working of God who raised him from the dead’ (Romans 6:4)” (Second Vatican Council, Decree on Ecumenism, 22) (John Hardon, The Question and Answer Catholic Catechism (Garden: Image, 1981).