Baptism is the rite which admits a candidate into the Christian Church, and is considered a sacrament by most denominations. The paradigmatic baptism is that of Jesus himself. As recounted in the Gospels, Jesus was baptized by John the Baptist in the River Jordan; after Jesus emerged from the water, the Holy Spirit descended upon him, in the form of a dove, and the voice of God spoke from heaven, declaring Jesus to be ‘my well-beloved son’. Hence the constituent elements of the baptismal rite are water and a Trinitarian formula: candidates are baptized in the name of the Father, Son, and Holy Spirit. According to Matthew's gospel, Jesus commanded his disciples to baptize thus in his post-resurrection appearance to them in Galilee.
The origins of Christian baptism are probably found in the initiation rites of Jewish proselytes and, possibly, those of the mystery religions. Various baptismal rites were developed in the early Church, all designed to bring some or all of the body into contact with the baptismal waters. They generally involved immersion. This usually meant standing in water and having water poured on one's head and upper body. Such rites might involve triple immersion (in the name of the Father, Son, and Holy Spirit) as outlined in the late-first-century practical teaching document, The Didache, in which Christians were instructed to baptize the candidate three times in running water or by pouring water over the head three times. The Apostolic Tradition, describing rites and practices in third-century Rome, stated that the baptismal candidates should remove their clothes and enter the waters of the baptistry, where they would be baptized in the name of the Father, Son, and Holy Spirit. Having been anointed with chrism (see below), they would put their clothes back on and enter the church to participate in the Eucharist for the first time.
Baptism was quickly seen as necessary for salvation and as the initial moment of redemption; many passages in Acts teach that baptism must be preceded by faith and the confession and renunciation of sins. Paul developed a theology of baptism in which believers, being baptized, come to union with Christ, share in His death and resurrection, are cleansed of their sins, and incorporated into the body of Christ. The believer's sins are metaphorically washed away in the rite. The water is the visible sign of God's grace.
Preparation for baptism in the early Church was serious and lengthy — it could take up to three years. Many public officials in the early Church, and in early Christendom especially, postponed baptism until the end of their lives, knowing that they would be ‘sullied’ by the activities of their public life. Early creeds developed as simple formulae of Christian belief to be used in the baptismal rite. In the first two centuries, bishops, priests, and deacons (all of whom could be women or men) conferred baptism, but gradually, as the bishop's role was expanded, and women were squeezed out of all of these ministerial positions, it came to be the bishop who baptized. In cases of necessity, baptism could be conferred by anyone — and thus, right through the Middle Ages and into the modern period, it was often the midwife who performed the baptismal rite when a newly-born baby's life was in danger. Easter and Pentecost were the traditional times for baptism, though some churches began to hold baptisms on other feasts, such as Epiphany or Christmas. Baptismal candidates have traditionally had sponsors or godparents to support them in the faith (who, in the case of infants, would accept Christ as the infant's saviour on his or her behalf).
Chrism — holy oil which is a mixture of olive oil and balsam, and consecrated by a bishop — is used in baptismal rites in Eastern Orthodox. Roman Catholic, and Anglican churches. It was used in early baptismal rites. Tradition has it that it is placed on the baptismal candidate's forehead, hands, and feet, to seal the points at which the devil might enter, but there are also understandings of chrism representing — by the richness of the oil and the sweetness of the balsam — the fullness of sacramental grace and the gifts of the Holy Spirit, as well as the sweetness of Christian virtue. John Chrysostom, in the fourth century, wrote of baptismal candidates being anointed with oil from the top of the hairs of the head down to the feet and thereby becoming sharers in the true olive tree, Jesus Christ, and being healed of every trace of sin. An old Roman Catholic baptismal rite involved the offering of blessed salt to the baptismal candidate; this was probably based on the pagan Roman custom of placing a few grains of salt on the lips of an infant, eight days after its birth, to chase away the demons. Salt, because of its preservative quality, represented purity and incorruptibility.
The early Church seems to have baptized both infants and adults (though there is debate amongst historians about this). Gradually, infant baptism came to be the norm in Christendom, especially as a doctrine of original sin developed. Thus baptism became one of the seven sacraments in the Roman Catholic church. At the Reformation, Luther, Zwingli, and Calvin all retained infant baptism, though they interpreted the theology of it differently from the Roman Catholic Church. The Anabaptists rejected infant baptism, advocating believers' baptism, a response of faith by the individual to the gospel.
Today, some Christians — notably Baptists and many Eastern Orthodox — practise full immersion, that is the dipping of the whole body, including the face, into the water. In most Western churches, water is poured or splashed onto the head three times.
— Jane Shaw