That which is born of the flesh is flesh. That which is born of the Spirit is spirit.
Secondly, Jesus Christ is able, and fit, and every way qualified, to reveal the will of God to us; for it is he that came down from heaven and is in heaven. He had said (John 3:12), How shall ye believe, if I tell you of heavenly things? Now here, 1. He gives them an instance of those heavenly things which he could tell them of, when he tells them of one that came down from heaven, and yet is the Son of man; is the Son of man, and yet is in heaven. If the regeneration of the soul of man is such a mystery, what then is the incarnation of the Son of God? These are divine and heavenly things indeed. We have here an intimation of Christ's two distinct natures in one person: his divine nature, in which he came down from heaven; his human nature, in which he is the Son of man; and that union of those two, in that while he is the Son of man yet he is in heaven. 2. He gives them a proof of his ability to speak to them heavenly things, and to lead them into the arcana of the kingdom of heaven, by telling them, (1.) That he came down from heaven. The intercourse settled between God and man began above; the first motion towards it did not arise from this earth, but came down from heaven. We love him, and send to him, because he first loved us, and sent to us. Now this intimates, [1.] Christ's divine nature. He that came down from heaven is certainly more than a mere man; he is the Lord from heaven, 1 Corinthians 15:47. [2.] His intimate acquaintance with the divine counsels; for, coming from the court of heaven, he had been from eternity conversant with them. [3.] The manifestation of God. Under the Old Testament God's favours to his people are expressed by his hearing from heaven (2 Chronicles 7:14), looking from heaven (Psalms 80:14), speaking from heaven (Nehemiah 9:13), sending from heaven, Psalms 57:3. But the New Testament shows us God coming down from heaven, to teach and save us. That he thus descended is an admirable mystery, for the Godhead cannot change places, nor did he bring his body from heaven; but that he thus condescended for our redemption is a more admirable mercy; herein he commended his love. (2.) That he is the Son of man, that Son of man spoken of by Daniel (John 7:13), by which the Jews always understand to be meant the Messiah. Christ, in calling himself the Son of man, shows that he is the second Adam, for the first Adam was the father of man. And of all the Old-Testament titles of the Messiah he chose to make use of this, because it was most expressive of his humility, and most agreeable to his present state of humiliation. (3.) That he is in heaven. Now at this time, when he is talking with Nicodemus on earth, yet, as God, he is in heaven. The Son of man, as such, was not in heaven till his ascension; but he that was the Son of man was now, by his divine nature, every where present, and particularly in heaven. Thus the Lord of glory, as such, could not be crucified, nor could God, as such, shed his blood; yet that person who was the Lord of glory was crucified (1 Corinthians 2:8), and God purchased the church with his own blood, Acts 20:28. So close is the union of the two natures in one person that there is a communication of properties. He doth not say hos esti. God is the ho on to ourano—he that is, and heaven is the habitation of his holiness.