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.
The wonder of Nicodemus being roused again by the words, He who is born of the Spirit is spirit, Christ meets him again with an instance from nature; Marvel not that I said unto thee, Ye must be born again. The expression, Marvel not, shows that Nicodemus was surprised at His doctrine. He takes for this instance some thing, not of the grossness of other bodily things, but still removed from the incorporeal nature, the wind; 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. That is to say, if no one can restrain the wind from going where it will; much less can the laws of nature, whether the condition of our natural birth, or any other, restrain the action of the Spirit. That He speaks of the wind here is plain, from His saying, Thou hearest the sound thereof, i. e. its noise when it strikes objects. He would not in talking to an unbeliever and ignorant person, so describe the action of the Spirit. He says, Bloweth where it listethc; not meaning any power of choice in the wind, but only its natural movements, in their uncontrolled power. But canst not tell whence it cometh or whither it goeth; i. e. If thou canst not explain the action of this wind which comes under the cognizance both of thy feeling and hearing, why examine into the operation of the Divine Spirit? He adds, So is every one that is born of the Spirit.
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.
[AD 367] Hilary of Poitiers on John 3:7-8