The practice of baptism was a common rite of initiation in many religious expressions in the ancient Mediterranean world. From the time of Jesus, Christianity also expressed through water baptism freedom from sin, union with Jesus Christ and all other baptized persons, our participation in the salvific death and resurrection of Jesus and our new life in the Spirit.

St. Paul, the first great theologian of baptism, expressed its meaning in terms of a break with the old and beginning of new life in Christ. He understood well the reality of the relationship that baptism establishes between us and God and his Son Jesus. The New Testament provides the basis and focal point for the Church’s understanding of baptism.

Jesus’ own baptism, to which all four Gospels make reference (John less directly than the other three), provides a starting point for any serious study of the sacrament.

Contrary to some writers’ opinions, Jesus’ baptism was not simply an affirmation of his messiahship, but rather a proclamation of his relationship as Son to the Father. In the baptismal scene in the Gospel of Mark, for example, God speaks directly to Jesus: "You are my Son, the Beloved; with you I am well pleased" (Mark 1:11). In Matthew, the voice addresses the crowd: "This is my Son, the Beloved, with whom I am well pleased" (Matthew 3:17). In Luke, again the voice is directed to Jesus: "You are my Son, the Beloved; with you I am well pleased" (Luke 3:22).

Here we find the basis for the meaning of baptism as the ritual in which one becomes a child of God. Just as Jesus is God’s Son, so also the baptized person is a daughter or son of God and is called by God to take on the family resemblance in living and loving as Jesus did.
In the Fourth Gospel, John the Baptist witnesses to Jesus’ identity as God’s Son: "And I myself have seen and have testified that this is the Son of God" (John 1:34). His sonship is affirmed by the Spirit who rests on him (John 1:32). John the Baptist proclaims him to be the "Lamb of God" who destroys the world’s sin through his death and resurrection. John thus affirms that the action of choosing is of God. St. Paul speaks of God’s choosing us before the foundation of the world (Ephesians 1:4). Hence baptism is not our choice or our achievement but an election by God.

The role of the Spirit in baptism is attested by all three Synoptic Gospels. The Spirit is the greatest gift of Jesus in baptism. John declares, "I have baptized you with water; but he will baptize you with the Holy Spirit" (Mark 1:8; see also Matthew 3:11; Luke 3:16).
Two passages concerning the waters of baptism stand out in the Gospel according to John. The first is a statement by Jesus to Nicodemus: "Very truly, I tell you, no one can enter the kingdom of God without being born of water and the Spirit" (John 3:5). The other is the story of the man born blind in John 9:1-41. Jesus tells the man to go and wash in the pool of Siloam, and the evangelist tells us that "Siloam" means "the one sent." In other words, the blind man is to wash himself in the person of Jesus who was sent by the Father.

Acts of the Apostles adds to our understanding of baptism with references to belief in Jesus, which is the heart and basis for baptism. Paul’s account of his conversion in Acts is a good example.
Ananias says to Paul, "Brother Saul, regain your sight!" Paul tells us, "In that very hour I regained my sight and saw him. Then he said, ‘The God of our ancestors has chosen you to know his will, to see the Righteous One and to hear his own voice; for you will be his witness to all the world of what you have seen and heard. And now why do you delay? Get up, be baptized, and have your sins washed away, calling on his name’" (Acts 22:13-16).

Thus Acts of the Apostles associates baptism with the Holy Spirit and his gifts of salvation, belief in Jesus and God, preaching the Good News and repentance of sin. Clearly, both in the Gospels and in Acts, baptism is never simply a private matter. Baptism is always between Jesus and the person baptized, but at the same time, it is an act of the Church with Jesus as its center.

In Paul’s letters, we find a more developed theological understanding of baptism, even though it is generally agreed that Paul’s letters preceded the writing of the Gospels. However, the sources used by the evangelists concerning the baptism of Jesus predate Paul’s letters and hence would reflect an earlier understanding on which Paul himself built.

Paul speaks of the transformation through the power of the Spirit that occurs in baptism: "And this is what some of you used to be. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and in the Spirit of our God" (1 Corinthians 6:11). Thus Paul emphasizes the dignity to which a person rises in baptism: "Or do you not know that your body is a temple of the Holy Spirit within you, which you have from God, and that you are not your own?" (1 Corinthians 6:19). Baptism, therefore, raises the person to a dignity that God will never deny; once a chosen child of God, one always remains God’s dearly loved child.

St. Paul tells us that the baptized person is one with the Lord: "But anyone united to the Lord becomes one spirit with him" (1 Corinthians 6:17). So intimate is this union with the risen Lord, Paul says, that "if we have been united with him in a death like his, we will certainly be united with him in a resurrection like his" (Romans 6:5). The Greek word for "united," symphytos, is a horticulture word that means "grafted." In other words, Paul is saying that like a grafted shoot, the baptized person is so closely united with Christ that he or she derives life from Jesus Christ himself. Thus baptism marks the end of the power of sin for the baptized, so that the believer lives a new kind of life for God in Christ, to whom he or she is intimately united. Baptism communicates to the believer the life-giving power of the risen Lord.

That union with Christ, however, is not individualistic but rather a corporate one, for the Christian is one with all other believers: "[L]ead a life worthy of the calling to which you have been called, ... making every effort to maintain the unity of the Spirit in the bond of peace. There is one body and one Spirit, ... one Lord, one faith, one baptism, one God and Father of all" (Ephesians 4:1-4).

Paul states that in baptism, "[I]f you belong to Christ, then you are Abraham’s offspring, heirs according to the promise" (Galatians 3:29). By the waters of baptism, the Christian enters into the fullness of salvation history. Merely by belonging to Christ, one becomes an heir of the promises made to Abraham. "[I]n Christ Jesus you are all children of God through faith. As many of you as were baptized into Christ have clothed yourselves with Christ. There is no longer Jew or Greek, there is no longer slave or free, there is no longer male and female; for all of you are one in Christ Jesus" (Galatians 3:26).

That which happened to Christ in his death and resurrection is transferred to the believer in baptism: "Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? Therefore we have been buried with him by baptism into death, so that, just as Christ was raised from the dead by the glory of the Father, so we too might walk in newness of life" (Romans 6:3-4).

Water as a symbol of baptism is rich and meaningful. Water refreshes, cleanses and gives life. Many adults remember that as children receiving religious instruction, the emphasis in the study of baptism was on the removal of original sin.

A frequently asked question was, "How can God punish me for something I did not do?" When speaking of original sin, we are not referring to personal fault but rather to an inclination to evil, a deprivation of holiness and likeness to our Creator. This deprived condition, which we call original sin, is the result of Adam and Eve's loss of their gift of holiness and friendship with God. Like their first parents, all human beings share this loss and are subject to suffering, death and ignorance.

Christ, however, conquered the power of Satan by his death and resurrection. St. Paul says, "Just as one man's trespass led to condemnation for all, so one man's act of righteousness leads to justification and life for all" (Romans 5:18).
In baptism, we are reoriented toward God; the life of grace overcomes the power of evil and enables the baptized to believe in God and to engage, under the power of the Holy Spirit, in the struggle against Satan and the power of death.

Water also has the power to take away life. In baptism, the person dies to all that is not of Christ and rises to new life with him: "Therefore we have been buried with him by baptism into death, so that, just as Christ was raised from the dead by the glory of the Father, so we too might walk in newness of life" (Romans 6:4).

Out of God’s revealed word, the Church has developed a theology of baptism that takes into account the lived experience of the Church throughout its history, its liturgical life and its theological developments.
The notion of baptism as a sacrament dates back to the early centuries of Christianity. The word "sacrament" is borrowed from the Latin, sacramentum, which in Roman times referred to an initiation rite in which soldiers promised their fidelity to their commander. In teaching Gentiles, the Church used the word sacramentum to explain the rite of Christian initiation in which the initiates would commit themselves to the service of God. When Christianity supplanted polytheism in the empire, the Roman sense was dropped, and the word was expanded to any symbol that represented one’s relationship to God.

By the fifth century, St. Augustine referred to a sacramentum as anything that was "a sign of a sacred reality." By the twelfth century, the word was restricted to the seven rituals of the Church which Catholics refer to as the seven sacraments.

In the first century, however, the word "baptism" was not specifically a Christian designation for a sacrament. The ancient mystery religions made use of initiation rites which had similarities to Jewish and Christian baptisms. Hebrews 6:1-2 speaks of "baptisms" that were practiced by the Jews before the resurrection of Jesus. These baptisms were largely purification rites. By the second century A.D., these Jewish rituals had developed into initiatory rites for proselytes and included instruction, circumcision and water baths. They were initiatory rites that made Gentiles Jews by purifying them from their state of uncleanness and admitting them into the covenant life of Judaism, which in turn was culminated by the offering of sacrifice.

The Church’s baptismal tradition has shaped the rite as we know it in the Catholic Church today. From the Church’s expression of corporate faith in the early Church, through conversion and a ritual that was aimed at sustaining one in the faith in the face of persecution and death, to its present ritual form, baptism continues to unite the baptized individual with Christ and his body, the Church.