Baptism is an ordinance of the New Testament, ordained by Jesus Christ, to be to the person who is baptized - a sign of his fellowships with Christ in His death and resurrection; of his being engrafted into Christ; of remission of sins; and of that person's giving up of himself to God, through Jesus Christ, to live and walk in newness of life. (1689 London Baptist Confession #29)
6 What shall we say then? Are we to continue in sin so that grace may increase?
2 May it never be! How shall we who died to sin still live in it?
3 Or do you not know that all of us who were baptized into Christ Jesus were baptized into His death?
4 Therefore we were buried with Him through baptism into death, so that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life.
5 For if we have become united with Him in the likeness of His death, certainly we shall also be in the likeness of His resurrection,
6 knowing this, that our old man was crucified with Him, in order that our body of sin might be done away with, so that we would no longer be slaves to sin;
7 for he who has died has been justified from sin.
8 Now if we died with Christ, we believe that we shall also live with Him,
9 knowing that Christ, having been raised from the dead, is never to die again; death no longer is master over Him.
10 For the death that He died, He died to sin once for all, but the life that He lives, He lives to God.
11 Even so consider yourselves to be dead to sin, but alive to God in Christ Jesus.
Ephesians 2:8-9, Luke 23:39-43, Romans 5:20-21, 2 Corinthians 5:17, Mark 10:38, Luke 12:50, John 1:12-13
"When it is applied to Christian initiation we ought not to think in terms of gentleness and inspiration; it means death, death to a whole way of life. It is this that is Paul's point here. Christians are people who have died, and their baptism emphasizes that death. We should not let the modern associations of baptism blind us to the point Paul is making so strongly. He is saying that it is quite impossible for anyone who understands what baptism means to aquiesce cheerfully in a sinful life. The baptized have died to all that." (Dr. Leon Morris)
"Baptism is not what saves us, but in our baptism God gives us a tangible sign of His promise of redemption. All the processes that are wrought through the redeeming work of Christ are contained in that sign. Baptism is a sign of our being regenerated by the Holy Spirit. It does not effect regeneration, but it is a sign of it. It is a sign of God's promise that all who believe will, in fact, be justified. It is a sign of our sanctification. It is a sign of our being indwelt by the Holy Spirit. It is a sign of our glorification. It is a sign of our identification with Christ. We are in Christ and He is our champion." (Dr. R.C. Sproul)