John 3:5
“Verily I say unto you, Unless a man be born of water and of the Spirit, he cannot enter into the Kingdom of God.”
1. Little children who go daily to their teachers receive their lessons, and repeat them, and never cease from this kind of acquisition, but sometimes employ nights as well as days, and this they are compelled to do for perishable and transient things. Now we do not ask of you who have come to age such toil as you require of your children; for not every day, but two days only in the week do we exhort you to hearken to our words, and only for a short portion of the day, that your task may be an easy one. For the same reason also we divide to you in small portions what is written in Scripture, that you may be able easily to receive and lay them up in the storehouses of your minds, and take such pains to remember them all, as to be able exactly to repeat them to others yourselves, unless any one be sleepy, and dull, and more idle than a little child.
Let us now attend to the sequel of what has been before said. When Nicodemus fell into error and wrested the words of Christ to the earthly birth, and said that it was not possible for an old man to be born again, observe how Christ in answer more clearly reveals the manner of the Birth, which even thus had difficulty for the carnal enquirer, yet still was able to raise the hearer from his low opinion of it. What says He? “Verily I say unto you, Unless a man be born of water and of the Spirit, he cannot enter into the Kingdom of God.” What He declares is this: “You say that it is impossible, I say that it is so absolutely possible as to be necessary, and that it is not even possible otherwise to be saved.” For necessary things God has made exceedingly easy also. The earthly birth which is according to the flesh, is of the dust, and therefore heaven is walled against it, for what has earth in common with heaven? But that other, which is of the Spirit, easily unfolds to us the arches above. Hear, you as many as are unilluminated, shudder, groan, fearful is the threat, fearful the sentence. “It is not (possible),” He says, “for one not born of water and the Spirit, to enter into the Kingdom of heaven”; because he wears the raiment of death, of cursing, of perdition, he has not yet received his Lord's token, he is a stranger and an alien, he has not the royal watchword. “Except,” He says, “a man be born of water and of the Spirit, he cannot enter into the Kingdom of heaven.”
Yet even thus Nicodemus did not understand. Nothing is worse than to commit spiritual things to argument; it was this that would not suffer him to suppose anything sublime and great. This is why we are called faithful, that having left the weakness of human reasonings below, we may ascend to the height of faith, and commit most of our blessings to her teaching; and if Nicodemus had done this, the thing would not have been thought by him impossible. What then does Christ? To lead him away from his groveling imagination, and to show that He speaks not of the earthly birth, He says, “Unless a man be born of water and of the Spirit he cannot enter into the Kingdom of heaven.” This He spoke, willing to draw him to the faith by the terror of the threat, and to persuade him not to deem the thing impossible, and taking pains to move him from his imagination as to the carnal birth. “I mean,” says He, “another Birth, O Nicodemus. Why do you draw down the saying to earth? Why do you subject the matter to the necessity of nature? This Birth is too high for such pangs as these; it has nothing in common with you; it is indeed called 'birth,' but in name only has it anything in common, in reality it is different. Remove yourself from that which is common and familiar; a different kind of childbirth bring I into the world; in another manner will I have men to be generated: I have come to bring a new manner of Creation. I formed (man) of earth and water; but that which was formed was unprofitable, the vessel was wrenched awry; I will no more form them of earth and water, but 'of water' and 'of the Spirit.'”
And if any one asks, “How of water?” I also will ask, How of earth? How was the clay separated into different parts? How was the material uniform, (it was earth only,) and the things made from it, various and of every kind? Whence are the bones, and sinews, and arteries, and veins? Whence the membranes, and vessels of the organs, the cartilages, the tissues, the liver, spleen, and heart? Whence the skin, and blood, and mucus, and bile? Whence so great powers, whence such varied colors? These belong not to earth or clay. How does the earth, when it receives the seeds, cause them to shoot, while the flesh receiving them wastes them? How does the earth nourish what is put into it, while the flesh is nourished by these things, and does not nourish them? The earth, for instance, receives water, and makes it wine; the flesh often receives wine, and changes it into water. Whence then is it clear that these things are formed of earth, when the nature of the earth is, according to what has been said, contrary to that of the body? I cannot discover by reasoning, I accept it by faith only. If then things which take place daily, and which we handle, require faith, much more do those which are more mysterious and more spiritual than these. For as the earth, which is soulless and motionless, was empowered by the will of God, and such wonders were worked in it; much more when the Spirit is present with the water, do all those things so strange and transcending reason, easily take place.
2. Do not then disbelieve these things, because you see them not; thou dost not see your soul, and yet you believe that you have a soul, and that it is a something different besides the body.
But Christ led him not in by this example, but by another; the instance of the soul, though it is incorporeal, He did not adduce for that reason, because His hearer's disposition was as yet too dull. He sets before him another, which has no connection with the density of solid bodies, yet does not reach so high as to the incorporeal natures; that is, the movement of wind. He begins at first with water, which is lighter than earth, but denser than air. And as in the beginning earth was the subject material, but the whole was of Him who molded it; so also now water is the subject material, and the whole is of the grace of the Spirit: then, “man became a living soul,”; now he becomes “a quickening Spirit.” But great is the difference between the two. Soul affords not life to any other than him in whom it is; Spirit not only lives, but affords life to others also. Thus, for instance, the Apostles even raised the dead. Then, man was formed last, when the creation had been accomplished; now, on the contrary, the new man is formed before the new creation; he is born first, and then the world is fashioned anew. And as in the beginning He formed him entire, so He creates him entire now. Then He said, “Let us make for him a help”, but here He said nothing of the kind. What other help shall he need, who has received the gift of the Spirit? What further need of assistance has he, who belongs to the Body of Christ? Then He made man in the image of God, now He has united him with God Himself; then He bade him rule over the fishes and beasts, now He has exalted our first-fruits above the heavens; then He gave him a garden for his abode, now He has opened heaven to us; then man was formed on the sixth day, when the world was almost finished; but now on the first, at the very beginning, at the time when light was made before. From all which it is plain, that the things accomplished belonged to another and a better life, and to a condition having no end.
Source: Homilies on the Gospel of John (New Advent)