Catechism of the Catholic Church
1272 Incorporated into Christ by Baptism, the person baptized is configured to Christ. Baptism seals the Christian with the indelible spiritual mark (character) of his belonging to Christ. No sin can erase this mark, even if sin prevents Baptism from bearing the fruits of salvation. 83 Given once for all, Baptism cannot be repeated.
1273 Incorporated into the Church by Baptism, the faithful have received the sacramental character that consecrates them for Christian religious worship. 84 The baptismal seal enables and commits Christians to serve God by a vital participation in the holy liturgy of the Church and to exercise their baptismal priesthood by the witness of holy lives and practical charity. 85
1274 The Holy Spirit has marked us with the seal of the Lord ("Dominicus character") "for the day of redemption." 86 "Baptism indeed is the seal of eternal life." 87 The faithful Christian who has "kept the seal" until the end, remaining faithful to the demands of his Baptism, will be able to depart this life "marked with the sign of faith," 88 with his baptismal faith, in expectation of the blessed vision of God - the consummation of faith - and in the hope of resurrection.
1275 Christian initiation is accomplished by three sacraments together: Baptism which is the beginning of new life; Confirmation which is its strengthening; and the Eucharist which nourishes the disciple with Christ's Body and Blood for his transformation in Christ.
1276 "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you" (Mt 28:19-20).
1277 Baptism is birth into the new life in Christ. In accordance with the Lord's will, it is necessary for salvation, as is the Church herself, which we enter by Baptism.
1278 The essential rite of Baptism consists in immersing the candidate in water or pouring water on his head, while pronouncing the invocation of the Most Holy Trinity: the Father, the Son, and the Holy Spirit.
1279 The fruit of Baptism, or baptismal grace, is a rich reality that includes forgiveness of original sin and all personal sins, birth into the new life by which man becomes an adoptive son of the Father, a member of Christ and a temple of the Holy Spirit. By this very fact the person baptized is incorporated into the Church, the Body of Christ, and made a sharer in the priesthood of Christ.
1280 Baptism imprints on the soul an indelible spiritual sign, the character, which consecrates the baptized person for Christian worship. Because of the character Baptism cannot be repeated (cf. DS 1609 and DS 1624).
1281 Those who die for the faith, those who are catechumens, and all those who, without knowing of the Church but acting under the inspiration of grace, seek God sincerely and strive to fulfill his will, can be saved even if they have not been baptized (cf. LG 16).
1282 Since the earliest times, Baptism has been administered to children, for it is a grace and a gift of God that does not presuppose any human merit; children are baptized in the faith of the Church. Entry into Christian life gives access to true freedom.
1283 With respect to children who have died without Baptism, the liturgy of the Church invites us to trust in God's mercy and to pray for their salvation.
1284 In case of necessity, any person can baptize provided that he have the intention of doing that which the Church does and provided that he pours water on the candidate's head while saying: "I baptize you in the name of the Father, and of the Son, and of the Holy Spirit."
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.