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 Ghost1, 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's2.
Scripture proofs
The Westminster Assembly's proof texts (KJV). The bracketed numbers in the answer above mark the clause each set of references supports; expand a row to read the verses.
1 Matt. 28:19
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
2 Acts 2:38-42; 22:16; Rom. 6:3-4; Gal. 3:26-27; 1 Pet. 3:21
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
Acts 2:39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the LORD our God shall call.
Acts 2:40 And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.
Acts 2:41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.
Acts 2:42 And they continued stedfastly in the apostles’ doctrine and fellowship, and in breaking of bread, and in prayers.
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
Rom. 6:3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
Rom. 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Gal. 3:26 For ye are all the children of God by faith in Christ Jesus.
Gal. 3:27 For as many of you as have been baptized into Christ have put on Christ.
The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ:
This doctrine across the Standards
Where the Confession and the Westminster Larger Catechism treat the same matter, so the question can be studied alongside its parallel statements.
In the Westminster Confession
XXVIII.1 Baptism is a sacrament of the New Testament, ordained by Jesus Christ, not only for the solemn admission …
Baptism is a sacrament of the New Testament, ordained by Jesus Christ, not only for the solemn admission of the party baptized into the visible Church, but also to be unto him a sign and seal of the covenant of grace, of his ingrafting into Christ, of regeneration, of remission of sins, and of his giving up unto God, through Jesus Christ, to walk in newness of life: which sacrament is, by Christ's own appointment, to be continued in his Church until the end of the world.
→ XXVIII.1 · Of BaptismXXVIII.2 The outward element to be used in this sacrament is water, wherewith the party is to be baptized …
The outward element to be used in this sacrament is water, wherewith the party is to be baptized in the name of the Father, and of the Son, and of the Holy Ghost, by a minister of the gospel lawfully called thereunto.
→ XXVIII.2 · Of BaptismXXVIII.3 Dipping of the person into the water is not necessary; but baptism is rightly administered by pouring or …
Dipping of the person into the water is not necessary; but baptism is rightly administered by pouring or sprinkling water upon the person.
→ XXVIII.3 · Of BaptismXXVIII.4 Not only those that do actually profess faith in and obedience unto Christ, but also the infants of …
Not only those that do actually profess faith in and obedience unto Christ, but also the infants of one or both believing parents are to be baptized.
→ XXVIII.4 · Of BaptismXXVIII.5 Although it be a great sin to contemn or neglect this ordinance, yet grace and salvation are not …
Although it be a great sin to contemn or neglect this ordinance, yet grace and salvation are not so inseparably annexed unto it, as that no person can be regenerated or saved without it, or that all that are baptized are undoubtedly regenerated.
→ XXVIII.5 · Of BaptismXXVIII.6 The efficacy of baptism is not tied to that moment of time wherein it is administered; yet, notwithstanding, …
The efficacy of baptism is not tied to that moment of time wherein it is administered; yet, notwithstanding, by the right use of this ordinance the grace promised is not only offered, but really exhibited and conferred by the Holy Ghost, to such (whether of age or infants) as that grace belongeth unto, according to the counsel of God's own will, in his appointed time.
→ XXVIII.6 · Of BaptismXXVIII.7 The sacrament of baptism is but once to be administered to any person.
The sacrament of baptism is but once to be administered to any person.
→ XXVIII.7 · Of BaptismIn the Westminster Larger Catechism
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, to be a sign and seal of ingrafting into himself, of remission of sins by his blood, and regeneration by his Spirit; of adoption, and resurrection unto everlasting life; and whereby the parties baptized are solemnly admitted into the visible church, and enter into an open and professed engagement to be wholly and only the Lord's.
→ Open Q.165Q.166 Unto whom is Baptism to be administered?
Baptism is not to be administered to any that are out of the visible church, and so strangers from the covenant of promise, till they profess their faith in Christ, and obedience to him, but infants descending from parents, either both, or but one of them, professing faith in Christ, and obedience to him, are in that respect within the covenant, and to be baptized.
→ Open Q.166Q.167 How is our Baptism to be improved by us?
The needful but much neglected duty of improving our Baptism, is to be performed by us all our life long, especially in the time of temptation, and when we are present at the administration of it to others; by serious and thankful consideration of the nature of it, and of the ends for which Christ instituted it, the privileges and benefits conferred and sealed thereby, and our solemn vow made therein; by being humbled for our sinful defilement, our falling short of, and walking contrary to, the grace of baptism, and our engagements; by growing up to assurance of pardon of sin, and of all other blessings sealed to us in that sacrament; by drawing strength from the death and resurrection of Christ, into whom we are baptized, for the mortifying of sin, and quickening of grace; and by endeavoring to live by faith, to have our conversation in holiness and righteousness, as those that have therein given up their names to Christ; and to walk in brotherly love, as being baptized by the same Spirit into one body.
→ Open Q.167