Church Fathers on John 3:6

Nicodemus coming to Jesus, as to a man, is startled on learning greater things than man could utter, things too lofty for him. His mind is darkened, and he does not stand firm, but reels like one on the point of falling away from the faith. Therefore he objects to the doctrine as being impossible, in order to call forth a fuller explanation. Two things there are which astonish him, such a birth, and such a kingdom; neither yet heard of among the Jews. First he urges the…

The question put thus sounds as if a boy might enter a second time into his mother’s womb and be born. But Nicodemus, we must remember, was an old man, and took his instance from himself; as if he said, I am an old man, and seek my salvation; how can I enter again into my mother’s womb, and be born?

It is the Spirit that speaks, whereas he understands carnally; he knew of no birth save one, that from Adam and Eve; from God and the Church he knows of none. But do you so understand the birth of the Spirit, as Nicodemus did the birth of the flesh; for as the entrance into the womb cannot be repeated, so neither can baptism.