And for this [rite] we have learned from the apostles this reason. Since at our birth we were born without our own knowledge or choice, by our parents coming together, and were brought up in bad habits and wicked training; in order that we may not remain the children of necessity and of ignorance, but may become the children of choice and knowledge, and may obtain in the water the remission of sins formerly committed, there is pronounced over him who chooses to be born again, and has repented of his sins, the name of God the Father and Lord of the universe; he who leads to the laver the person that is to be washed calling him by this name alone. For no one can utter the name of the ineffable God; and if any one dare to say that there is a name, he raves with a hopeless madness. And this washing is called illumination, because they who learn these things are illuminated in their understandings. And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Ghost, who through the prophets foretold all things about Jesus, he who is illuminated is washed.
Once the likeness painted on a panel has been effaced by stains from outside itself, the one whose likeness it is needs to come once more to enable the portrait to be renewed on the same wood. And, for the sake of his picture, even the mere wood on which it is painted is not thrown away, but the outline is renewed upon it. In the same way, the most holy Son of the Father, being the image of the Father, came to our world to renew humankind once made in his likeness. He came to find such lost individuals by the remission of their sins. He says as much himself in the Gospels: “I came to find and to save the lost.” This is why he also said to the Jews, “Except one be born again,” not meaning, as they thought, birth from a woman, but speaking of the soul born and created anew in the likeness of God’s image.
And indeed from the Spirit comes our new birth, and from the new birth our new creation, and from the new creation our deeper knowledge of the dignity of him from whom it is derived.
(Hom. xxiv. 1) As yet however he was withheld by Jewish infirmity: and therefore he came in the night, being afraid to come in the day. Of such the Evangelist speaks elsewhere, Nevertheless, among the chief rulers also many believed on Him; but because of the Pharisees they did not confess Him, lest they should be put out of the synagogue. (John 12:42)
(Hom. xxiv. 2. in Joan) He did not however conceive any great idea of them from His miracles; and attributed to Him as yet only a human character, speaking of Him as a Prophet, sent to execute a commission, and standing in need of assistance to do His work; whereas the Father had begotten Him perfect, selfsufficient, and free from all defect. It being Christ's design however for the present not so much to reveal His dignity, as to prove that He did nothing contrary to the Father; in words He is often humble, while His acts ever testify His power. And therefore to Nicodemus on this occasion He says nothing expressly to magnify Himself; but He imperceptibly corrects his low views of Him, and teaches him that He was Himself all-sufficient, and independent in His miraculous works. Hence He answers, Verily, verily, I say unto you, Except a man be born again, he cannot see the kingdom of God.
(Hom. xxiv. 2) He says therefore, Except a man be born again, he cannot see the kingdom of God: as if He said, Thou art not yet born again, i. e. of God, by a spiritual begetting; and therefore thy knowledge of Me is not spiritual, but carnal and human. But I say unto thee, that neither thou, nor any one, except he be born again of God, shall be able to see the glory which is around me, but shall be out of the kingdom: for it is the begetting by baptism, which enlightens the mind. Or the meaning is, Except thou art born from above, and hast received the certainty of my doctrines, thou wanderest out of the way, and art far from the kingdom of heaven. By which words our Lord discloses His nature, showing that He is more than what He appears to the outward eye. The expression, From abovea, means, according to some, from heaven, according to others, from the beginning. Had the Jews heard it, they would have left Him in scorn; but Nicodemus shows the love of a disciple, by staying to ask more questions.
Nicodemus saith, "Rabbi, we know that Thou art a Teacher come from God, for no man can do the miracles that Thou doest, except God be with him." He thought he had said something great when he had spoken thus of Christ. What then saith Christ? To show that he had not yet set foot even on the threshold of right knowledge, nor stood in the porch, but was yet wandering somewhere without the palace, both he and whoever else should say the like, and that he had not so much as glanced towards true knowledge when he held such an opinion of the Only-Begotten, what saith He?
"Verily, verily, I say unto thee, Except a man be born again, he cannot see the Kingdom of God."
That is, "Unless thou art born again and receivest the right doctrines, thou art wandering somewhere without, and art far from the Kingdom of heaven." But He does not speak so plainly as this. In order to make the saying less hard to bear, He does not plainly direct it at him, but speaks indefinitely, "Except a man be born again": all but saying, "both thou and any other, who may have such opinions concerning Me, art somewhere outside the Kingdom."
And this is why in many places Christ speaks obscurely, because He wishes to rouse His hearers to ask questions, and to render them more attentive. For that which is said plainly often escapes the hearer, but what is obscure renders him more active and zealous. Now what He saith, is something like this: "If thou art not born again, if thou partakest not of the Spirit which is by the washing of Regeneration, thou canst not have a right opinion of Me, for the opinion which thou hast is not spiritual, but carnal." But He did not speak thus, as refusing to confound one who had brought such as he had, and who had spoken to the best of his ability; and He leads him unsuspectedly up to greater knowledge, saying, "Except a man be born again." The word "again," in this place, some understand to mean "from heaven," others, "from the beginning." "It is impossible," saith Christ, "for one not so born to see the Kingdom of God"; in this pointing to Himself, and declaring that there is another beside the natural sight, and that we have need of other eyes to behold Christ.
[Jesus seems to be saying to him], “If you believe that I was sent as a teacher from God, and the miracles I accomplished convince you of this, as you say, our teaching then requires another way of life and expects the beginning of a new generation.” So we hope indeed to see the kingdom of God, because, while we are mortal, we cannot go there if we are not raised incorruptible after our death. We believe that this happens typologically through baptism: we are born again in an image of the resurrection, that is, of a new state [of being].
"Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God." Therefore to them who have been born again does Jesus trust Himself. Behold, those men had believed on Him, and yet Jesus trusted not Himself to them. Such are all catechumens: already they believe in the name of Christ, but Jesus does not trust Himself to them.
Therefore mark, my brethren, what answer this man who came to Jesus by night makes. Although he came to Jesus, yet because he came by night, he still speaks from the darkness of his own flesh. He understands not what he hears from the Lord, understands not what he hears from the Light, "which lighteth every man that cometh into this world." Already hath the Lord said to him, "Except a man be born again, he shall not see the kingdom of God."
In these words he supposes that he can attain complete piety, and imagines that it will be sufficient for his salvation, to marvel merely at those things which call for wonder: nought else but this does he seek. Calling him a Teacher from God, and a co-worker with Him, he does not yet know that He is by Nature God, nor understand the plan of the dispensation with Flesh, but still approaches as to a mere man, and hath but slight conception of Him.
[AD 165] Justin Martyr on John 3:3