Heidelberg Catechism – Lord’s Day 27
Q. Does merely the outward washing with water itself wash away?
A. No; for only the blood of Jesus Christ and the Holy Spirit cleanse us from all sins.
Q. Then why does the Holy Spirit call baptism the water of rebirth and the washing away of sins?
A. God does not speak in this way except for a strong reason. Not only does he teach us by Baptism that just as the dirt of the body is taken away by water, so our sins are removed by the blood and Spirit of Christ; but more important still, by the divine pledge and sign he wishes to assure us that we are just as truly washed from our sins spiritually as our bodies are washed with water.
Q. Are infants also to be baptized?
A. Yes, because they, as well as their parents, are included in the covenant and belong to the people of God. Since both redemption from sin through the blood of Christ and the gift of faith from the Holy Spirit are promised to these children no less than to their parents, infants are also by baptism, as a sign of the covenant, to be incorporated into the Christian church and distinguished from the children of unbelievers. This was done in the Old Covenant by circumcision. In the New Covenant baptism has been instituted to take its place.