Christian baptism is the means by which a person makes a public profession of faith and discipleship. In the waters of baptism, a person says, wordlessly, “I confess faith in Christ; Jesus has cleansed my soul from sin, and I now have a new life of sanctification.”
Very simply, baptism is an outward testimony of the inward change in a believer’s life. Christian baptism is an act of obedience to the Lord after salvation; although baptism is closely associated with salvation, it is not a requirement to be saved.
The Bible shows in many places that the order of events is
1) a person believes in the Lord Jesus and
2) he is baptized. This sequence is seen in Acts 2:41, “Those who accepted [Peter’s] message were baptized” (see also Acts 16:14–15).
Being submerged in the water represents death to sin, and emerging from the water represents the cleansed, holy life that follows salvation. Romans 6:4 puts it this way: “We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life.”