Augustine of Hippo
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.
(lib. i. de Bapt. per. c. 30) Because He does not say, Except a man be born again1 of water and of the Spirit, he shall not have salvation, or eternal life; but, he shall not enter into the kingdom of God; from this, some infer that children are to be baptized in order to be with Christ in the kingdom of God, where they would not be, were they not baptized; but that they will obtain salvation and eternal life even if they die without baptism, not being bound with any chain of sin. But why is a man born again, except tobe changed from his old into a new state? Or why doth the image of God not enter into the kingdom of God, if it be not by reason of sin?