Christ is the Prophet of God, through whom He addresses all revelation. He is the Priest of God, by whom all who are saved must come. He has their names written on His breastplate. He is the King of God, into whose hands He has put all flesh, to give eternal life to as many as He has given him by divine election. Biblical baptism is to confess Him before men as He is.
Baptism is because of forgiveness of sins.
Those who repent do so unto forgiveness of sins. As God grants repentance, such identify with Christ and His forgiveness already obtained through His blood, by water baptism.