There are at least three important reasons why a believer should submit to the ordinance of Christian baptism.
When a Christian is baptized in water he demonstrates a vital testimony to his community and to society at large. He is saying in effect “I have decided to follow Jesus; no turning back”. He is saying publicly that he believes that Jesus Christ is the Son of God.
There is no recorded exception in the New Testament. All Christians were baptized upon their conversion. It was not an option to be exercised. It is the completing element in the process of renewal.
Mark 16:16 “Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.”
It is commanded. In the Great Commission: Matthew 28:18-20 “Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing 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. And surely I am with you always, to the very end of the age.”
…Jesus is very explicit. All authority (the power of one whose will and commands must be obeyed by others) has been given to Jesus. Therefore disciples (followers of Jesus) are to be baptized in water. New Christians are to be taught to obey everything that has been commanded them. When we obey the command to be baptized we are showing our union with and commitment to Christ.