The main content of this gospel instructs us about true righteousness, that is, how to become children of God, obtain forgiveness of sins and eternal life. The most distinguished conclusion of the Savior is: "Unless one is born from above, he cannot enter the kingdom of God." Thus, by requiring a new birth, Jesus completely rejects the old birth in regard to the eternal life to be attained. Why is this? The first birth is sinful, cursed, deadly, miserable because of sin; but the other birth is holy, blessed and eternal. The first birth, however, also has its advantages, righteousness in civil works, reason and all kinds of temporal rewards of this life. But all these advantages contribute nothing to eternal life. In the present life they are useful and necessary, but no man can see the kingdom of God unless he is born again.
But how is man born again? Answer: "of water and the Spirit. Notice that the Savior prefixes the water. For it is the first thing our eyes see in this work. But what does water contribute to a new birth, especially to one that works forgiveness of sins, that gives true righteousness and eternal life? The water washes only the body. But these are highly spiritual gifts, which do not wash away the outer skin, but purify the heart and change the whole mind.
Know, therefore, first of all, that God Himself has ordained water; therefore, it need not be despised or abolished. God is a mighty God who can raise up children even from stones. And so He can also wash and purify through water, not our body and skin alone, but the spirit itself and the heart. On the other hand, he has not only ordained water, but also the spirit, which he will not give without water. In this connection, the elementary visible water is now
to a spiritual bath. A damp and cold element becomes a fire of the Holy Spirit, whereby the old evil nature is burned out, as it were, and a new one is awakened, brought forth and strengthened in its place. Therefore Paul calls it a bath of rebirth and renewal of the Holy Spirit. Although the first natural birth serves for bodily life, is adorned with civic virtues, limited by worldly laws, kept in order by good discipline, so that the civic society arises from it, which is also God's work and which He wants to be preserved, it nevertheless contributes as much as nothing to eternal life, which God has promised to the righteous in His law. For nature is polluted and corrupted by original sin. And even if it can be accustomed to virtue, it is still far from being righteous. It remains vicious and under the judgment of death, which sin entailed. Therefore, after this physical and sinful birth, we must be born again, not through our mortal parents, but through the Holy Spirit, through the eternal God. The means for this is water or baptism, as the sign of grace that God has ordained, so that we may be convinced of His gracious and good will, that through the blood of Christ all our stains of sin may be washed away.
(4) This is a wonderful doctrine, but it must be grasped by faith. For as it cannot be understood whence the wind cometh, nor how far it goeth, but the sound thereof is only heard: so also this new birth cannot be apprehended by any other means than by the word.
Comparison between the natural wind and the Holy Spirit.
(5) As the wind is something free, not bound to any place, person or time, so is the Holy Spirit. Just as the wind moves, drives, refreshes, and permeates everything, so it is also with the effects of the Holy Spirit.