Associating with Christ’s Sacrifice
Baptism is a process in which a person is briefly submerged in water with the understanding that this is the gateway to an association with Christ Jesus.
The process and meaning of baptism are described in Romans 6.
"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 by the glory of the Father, we too might walk in newness of life." (Romans 6:3,4)
Baptism is the immersion of a believer in water. This follows the picture of burial - the person baptized is buried in water (which symbolises the death of Jesus) and then emerges from the water in the same way that Jesus emerged from the grave. In doing this the believer becomes part of the death of Jesus - the death of Jesus has become representative of the death of the believer, and the believer has new life because of this.
By baptism we become associated with the death of Jesus. Jesus now represents us, and as a result we also can take part in a resurrection. This is the point of the next verse:
"For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his."
The point here is that we don’t receive eternal life immediately; what we receive is a promise that we too will be raised to life by a resurrection, just as Jesus was. This is the resurrection at the day of judgement, when Jesus returns.
The passage continues a little further on with a summary:
"Now if we have died with Christ, we believe that we will also live with him." (Romans 6:8)
This reminds us that in baptism we die, in symbol, with Jesus but that later we will live with him in reality, at the day of judgement.
The whole process is summarised in the last verse of the chapter:
"For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord." (Romans 6:23)
The whole point of the death and resurrection of Jesus is to ensure that we can receive the forgiveness of our sins and by this find eternal life. To achieve this we need to be associated with his death and resurrection. This, of course, is the purpose of baptism.