John 3:7

Though I have received faith by my regeneration, I am still in ignorance. And yet, I have a firm hold on a reality I do not understand. I am born again, capable of rebirth, but without conscious perception of it. Moreover, the Spirit has no limits. He speaks when he wants, what he wants and where he wants. We are conscious of his presence when he comes, but the reason for his approach or his departure remains unknown to us.

Christ then having said, "He that is born of the Spirit is spirit," when He saw him again confused, leads His discourse to an example from sense, saying, "Marvel not that I said unto thee, Ye must be born again. The wind bloweth where it listeth." For by saying, "Marvel not," He indicates the confusion of his soul, and leads him to something lighter than body. He had already led him away from fleshly things, by saying, "That which is born of the Spirit is spirit"; but when Nicodemus knew not what "that which is born of the Spirit is spirit" meant, He next carries him to another figure, not bringing him to the density of bodies, nor yet speaking of things purely incorporeal, (for had he heard he could not have received this,) but having found a something between what is and what is not body, namely, the motion of the wind, He brings him to that next.

Seeing that Nicodemus is still troubled, He says: "Do not marvel." Then He attempts to teach by a sensible example.

Above, in his instruction on spiritual generation, the Lord presented a reason; here he gives an example. For we are led to see that Nicodemus was troubled when he heard that what is born of Spirit is itself spirit. And so the Lord says to him, Do not be surprised that I said to you, you must be born again.

Here we should note that there are two kinds of surprise or astonishment. One is the astonishment of devotion in the sense that someone, considering the great things of God, sees that they are incomprehensible to him; and so he is full of astonishment: "The Lord on high is wonderful" (Ps 92:4), "Your testimonies are wonderful" (Ps 118:129). Men are to be encouraged, not discouraged, to this kind of astonishment. The other is the astonishment of disbelief, when someone does not believe what is said. So Matthew (13:54) says: "They were astonished," and further on adds that "They did not accept him." It is from this kind of astonishment that the Lord diverts Nicodemus when he proposes an example.

Here is the paradox of Christianity. As practical imperatives for here and now the two great commandments have to be translated "Behave as if you loved God and man." For no man can love because he is told to. Yet obedience on this practical level is not really obedience at all. And if a man really loved God and man, once again this would hardly be obedience; for if he did, he would be unable to help it. Thus the command really says to us, "Ye must be born again." Till then, we have duty, morality, the Law. A schoolmaster, as St. Paul says, to bring us to Christ.