Let me combine the definitions of baptism from the London Baptist Confession (1689) and the Westminster Confession as a starting point to answer this question.
Baptism is an ordinance or sacrament of the New Testament, ordained by Jesus Christ and given to the church, to the person baptized, as a sign of the New Covenant; a sign of his fellowship with him, in his death and resurrection; of his being engrafted into him; of remission of sins; and of giving up into God, through Jesus Christ, to live and walk in newness of life.
I want to break this description down so that we can gain a fuller understanding of the meaning of baptism.
First, baptism is commanded by Christ but it is not necessary for salvation. Our salvation takes place at the point of saving faith. Baptism is a response of obedience to Christ; an additional step of faith for all who believe in him and are part of his church. If our faith is true and our desire for obedience real, then we will desire baptism.
Second, it is an ordinance or sacrament of the New Testament ordained by Christ. I understand that these terms have differences of meaning, but I am comfortable with both of them so I am using them both. I like the term ‘ordinance’ because it emphasizes that baptism was ordained by Christ. I like the word ‘sacrament’ because it highlights the covenantal and holy nature of baptism and emphasizes that it should not be taken lightly. Baptism is one of the means of grace given to the church. This means that through baptism God conveys grace to his people - both the one baptized and the ones watching - aiding them in their spiritual walk. This does not happen simply on account of a person getting into the water and being dunked, but on account of the Holy Spirit working mysteriously through baptism to bring blessing to the individual being baptized. So when there is genuine faith on the part of the one being baptized the Holy Spirit uses baptism and all that it symbolizes to encourage the faith of the one being baptized as well as the entire congregation of God’s people.
Third, it is an ordinance to be administered by the church. Baptism is given to the church as part of its mission to make disciples (cf Matthew 28:19-20; 1 Corinthians 12:13) It is also a sign of entrance into the body of Christ, the church. While we at CRC do not tie formal church membership together with baptism, we do recognize that participating in baptism includes with it a recognition by the individual of their obligation of living in discipleship with others in the church. This is why we don’t baptize people in their homes or apart from the meeting of the local church. Baptism is as much for the person in the water as it is for the people watching. It encourages and uplifts all of us.
Fourth, the fundamental symbolism of baptism is on the fellowship of the person with Christ in his death and resurrection. Baptism is a sign of what God has done in Christ to provide forgiveness of sins. It symbolizes in the life of the believer that through faith she has been brought from death to life and been granted forgiveness of sins upon their coming to Christ by faith. This is why we believe baptism should be done only to confessing believers. This is why what we practice is called credo-baptism; it is baptism upon confession of personal faith. Being immersed in water and then coming up out of it symbolizes physically what has been done spiritually when the believer was brought from death to life on account of the work of Christ on his behalf received by faith. Romans 6:3-4 clearly shows this relationship,
"Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead be the glory of the Father, we too might walk in newness of life."
Colossians 2:12 is also important,
"You were buried with him in baptism, in which you were also raised with him through faith in the working of God, who raised him from the dead.”
Fifth, baptism is a sign of the believers union with Christ and everything that entails. Not only is baptism a sign of our initial justification and the promise of eternal salvation, it is also a sign of our being brought into union with Christ through which we receive all of the blessings associated with our salvation. Notice what the fuller context of the above passage in Romans 6 (verses 1-10) highlights. This is an incredibly encouraging passage. In these 10 verses, and others in the New Testament, we realize that on account of our union with Christ, symbolized by our baptism, we have received an overwhelming number of blessings from him - we are a new creation, we have escaped divine judgment (cf 1 Peter 3:20-21), we are now his sons (Galatians 3:26-28), we receive his victory over sin, we are not free not to sin, we are given freedom from the sting of death and we are promised resurrection life in the future. Greg Allison summarizes these realities well. Baptism “associates the new Christian with the triune God - Father, Son and Holy Spirit. It vividly portrays identification with the death, burial, and resurrection of Jesus Christ. It clearly pictures cleansing from sin. It vividly depicts escape from divine judgment. And it signals entrance into the new covenant community.”
Last, because of what it is and means, baptism is to be done only to those who demonstrate a credible profession of faith. The overwhelming witness of Scripture is to the fact that baptism is only to be given to those who are old enough to profess true faith in Christ. Thus we should not baptize infants. But at what age is a person old enough to receive baptism upon confession of their faith? That will have to wait until our next blog.
Soli Deo Gloria