WSC Q.94: What is baptism?
Baptism is a sacrament, wherein the washing with water in the name of the Father, and of the Son, and of the Holy Ghost, (Matt. 28:19) doth signify and seal our ingrafting into Christ, and partaking of the benefits of the covenant of grace, and our engagement to be the Lord’s. (Rom. 6:4, Gal. 3:27)
WLC Q.165: What is Baptism?
Baptism is a sacrament of the New Testament, wherein Christ hath ordained the washing with water in the name of the Father, and of the Son, and of the Holy Ghost, (Matt. 28:19) to be a sign and seal of ingrafting into himself, (Gal. 3:27) of remission of sins by his blood, (Mark 1:4, Rev. 1:5) and regeneration by his Spirit; (Tit. 3:5, Eph. 5:26) of adoption, (Gal. 3:26–27) and resurrection unto everlasting life; (1 Cor. 15:29, Rom. 6:5) and whereby the parties baptized are solemnly admitted into the visible church, (1 Cor. 12:13) and enter into an open and professed engagement to be wholly and only the Lord’s. (Rom. 6:4)
WCF 28.1.
Baptism is a sacrament of the new testament, ordained by Jesus Christ, (Matt. 28:19) not only for the solemn admission of the party baptized into the visible Church; (1 Cor. 12:13) but also to be unto him a sign and seal of the covenant of grace, (Rom. 4:11, Col. 2:11–12) of his ingrafting into Christ, (Gal. 3:27, Rom. 6:5) of regeneration, (Tit. 3:5) of remission of sins, (Mark 1:4) and of his giving up unto God, through Jesus Christ, to walk in newness of life. (Rom. 6:3–4) Which sacrament is, by Christ’s own appointment, to be continued in His Church until the end of the world. (Matt. 28:19–20)