ANSWER: Because it is a commandment of God (Acts 2:38), which when obeyed from the heart results in freedom from sin (Romans 6:16-18) and puts us “into” Christ (Romans 6:3) wherein salvation is to be found (II Timothy 2:10). It is the final act of obedience which results in our salvation (Mark 16:16), and by which we are added to the church of the Bible (Acts 2:47). Without obedience to baptism (an immersion in water), none of these blessings would be ours!