John Chrysostom
Catena Aurea · Johannesevangelium 3
Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born? Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. Marvel not that I said unto thee, Ye must be born again. The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth; so is every one that is born of the Spirit.
(Hom. xxiv. 3) 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 former difficulty, as being the greatest marvel. Nicodemus saith unto him, How can a man be born when he is old? can he enter a second time into his mother’s womb, and be born?