Heidelberg # 73

Then why does the Holy Spirit call baptism the water of rebirth and the washing away of sins?

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.