Symbolically, our baptism imitates what our Savior did for us, and therefore, by our participation in it, we show our desire to be united—at one—with Him in both His death and resurrection (Romans 6:5). Paul writes in Galatians 2:20: "I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me." This is what our decision to be baptized tells our Father in heaven.
Being put into the water represents the death of the "old man" with his sinful way of life. Being completely covered by water symbolizes burial, and being raised from the water pictures a resurrection to "newness of life." After baptism we consider ourselves dead to sin, that is, we have completely divorced ourselves from living a sinful way of life (Romans 6:11). Once baptized, we are to give our lives to God and use our time to become "instruments of righteousness to God" (verse 13).
Richard T. Ritenbaugh
Basic Doctrines: Water Baptism