John Calvin on John 3:9

9. How can these things be? We see what is the chief obstacle in the way of Nicodemus. Every thing that he hears appears monstrous, because he does not understand the manner of it; so that there is no greater obstacle to us than our own pride; that is, we always wish to be wise beyond what is proper, and therefore we reject with diabolical pride every thing that is not explained to our reason; as if it were proper to limit the infinite power of God to our poor capacity. We are, indeed, permitted, to a certain extent, to inquire into the manner and reason of the works of God, provided that we do so with sobriety and reverence; but Nicodemus rejects it as a fable, on this ground, that he does not believe it to be possible. On this subject we shall treat more fully under the Sixth Chapter.