In Matt. 28:19 Jesus said, "...go and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit and teaching them to obey everything I have commanded you..." Although Jesus was perfectly sinless, He was baptised to fulfill all righteousness (Matt 3:15) and we also need to be baptised, if we are to follow in His footsteps and be obedient. 1 Pet. 3:21 describes baptism as an act of obedience where it says that it is “... the pledge of a good conscience toward God ...” Romans 6 explains how the act of being baptised is our pledge, our commitment, to enter into a new life in Christ. During baptism we commit to dying to sin and self and rising to a new life of obedience, no longer slaves to sin but slaves to righteousness.
Baptism doesn't save us nor does it bring forgiveness of sins as we are saved the moment we repent and turn to Jesus for forgiveness. Eph 1:13-14 say, "you also were included in Christ when you heard the word of truth, the gospel of your salvation. Having believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God's possession".These verses show that we receive the guarantee of our salvation, the Holy Spirit, as soon as we believe (John 1:12).
Baptism is often considered to be simply a public confession of faith but this falls short of its description in Rom 6:1-14. In this passage, baptism is described as an identification with Jesus' death (Rom. 6:3) and dying to self as He did. Jesus said in Luke 12:50, "I have a baptism to undergo, and how distressed I am until it is completed" and in Mark 10:39 He told His disciples, "You will drink the cup I drink and be baptized with the baptism I am baptized with." The baptism He was speaking of was His voluntary death on the cross through absolute surrender and total denial of Himself. He was perfectly sinless and denied Himself entirely to do His Father's will. If we are to do God's will and unite with Jesus in His resurrection (Php 3:10-11) then we too must die to self through the crucifixion and burial of our sinful nature (Rom. 6:3-7). In the passage Luke 14:26-33, Jesus spoke of total surrender and in the last verse He said, "In the same way, any of you who does not give up everything he has cannot be my disciple." Therefore, in the same way that Jesus died to self to do His Father's will, we must undergo a baptism of death to self, if we are to be His disciple. In baptism we identify ourselves with Jesus' death and resurrection; as we go under the water we figuratively unite with Him in death and as we come out of the water we are to rise to new life - dead to sin and self and fully surrendered to do His will (Rom. 6:4, 7, 11). Note Rom 6:22-23 which say, "... you have been set free from sin and have become slaves to God ... the benefit you reap leads to holiness and the result is eternal life ...".
The baptism of Romans 6 speaks of a believer's experience from the time of baptism onward. It is talking about a lifelong death to sin and self which is the process of sanctification. Note that Rom. 6:5, 8 say, "if we have been united",and "if we died with Christ". This indicates that not all those being spoken to had yet been "crucified with him" and "freed from sin" as it says in Rom. 6:6-7. Rom. 6:11-13 exhort believers "count yourselves dead to sin ... do not to let sin reign in your mortal bodies ... do not offer the parts of your body to sin ... but rather offer your body to God ... as instruments of righteousness." Rom. 6:15-23 continue on to talk about becoming slaves to righteousness which is the result of dying to self.It can be seen that baptism continues beyond the point of water baptism to be an ongoing crucifixion of self, resulting in a holy walk. In His prayer for the disciples just before He was crucified, Jesus said, "I sanctify myself, that they too may be truly sanctified" (John 17:19).On the cross, He set Himself apart entirely to do His Father's will so that through Him we too can set ourselves apart, take up our cross, die to self and be sanctified to do His will. So, with the little time we have on this earth, let us not miss the Grace of God. Let us strive to be to Jesus what He was to His Father ... fully committed, even to death.
As already mentioned, getting baptised won't save a person as salvation is an internal act of repentance and trust, not an external washing - see 1 Pet. 3:21 (The principle of baptism is similar to that of circumcision as described in Col 2:11-12 and Rom 2:25-29). If an unrepentant person does get baptised then he will get wet, but not saved. Also, note Romans 8:12-13 which says to Christians, "Therefore, brothers, we have an obligation - but it is not to the sinful nature ... for if you live according to the sinful nature, you will die, but if by the Spirit you put to death the misdeeds of the body, you will live." This is a clear warning to Christians, baptised or not, that they can lose their salvation. Because a believer can lose his salvation, it is clear that baptism does not seal a person's eternal future. The Bible makes it very clear that to be saved a person must be born again into newness of life and must walk in holiness if they are to inherit eternal life. For a discussion on this, please go to Perseverance Of The Saints.