1 There was a man of the Pharisees, named Nicodemus, a ruler of the Jews:

[Nicodemus, a ruler of the Jews] One of the members of the grand Sanhedrin; for such were ordinarily called rulers of the Jews. A person of the name of Nicodemus, the son of Gorion, is mentioned in the Jewish writings, who lived in the time of Vespasian, and was reputed to be so rich that he could support all the inhabitants of Jerusalem for ten years. But this is said in their usual extravagant mode of talking.

2 The same came to Jesus by night, and said unto him, Rabbi, we know that thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him.

[Came to Jesus by night] He had matters of the utmost importance on which he wished to consult Jesus Christ; and he chose the night season, perhaps less through the fear of man than the desire to have Jesus alone, as he found him all day encompased with the multitude so that it was impossible to speak fully on these weighty affairs.

[Rabbi] My master or teacher, a title of respect, something like our Doctor of Divinity, i.e. teacher of Divine things.

[We know that thou art a teacher come from God] We, all the members of the grand Sanhedrin, and all the rulers of the people, who have paid proper attention to your doctrines and miracles. We are all convinced of this though we are not all candid enough to admit it. Also, it is generally acknowledged among the populace that you are a teacher come from God.

[No man can do these miracles] It is on the evidence of your miracles that I ground my opinion of uou. No man can do what you do, unless the omnipotence of God be with him.

3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.

[Jesus answered] But what connection is there between our Lord's reply and the address of Nicodemus? Probably our Lord saw that the object of his visit was to inquire about the Messiah's kingdom (the anticipated arrival of the Messiah and the earthly kingdom which he was expected to establish) and in reference to this he immediately says, "Except a man be born again...". The repetition of amen, or verily, verily, among the Jewish writers was considered of equal import with the most solemn oath.

[Be born again] The birth for which Christ contends is from above - by the agency of the Holy Spirit. Every man must have two births, one from earth, the other from heaven - one of his body, the other of his soul; without the first he cannot see nor enjoy this world, without the last he cannot see nor enjoy the kingdom of God.
As there is an absolute necessity that a child should be born into this world, that he may see its light, contemplate its glories and enjoy its good, so there is an absolute necessity that the soul should be brought out of its state of darkness and sin, that it may be able to see, or to discern, the glories and excellencies of the kingdom of Christ here, and be prepared for the enjoyment of the kingdom of glory hereafter.
The new birth which is here spoken of comprehends, not only what is termed justification or pardon, but also sanctification or holiness. Sin must be pardoned, and the impurity of the heart washed away, before any soul can possibly enter into the kingdom of God. As this new birth implies the renewing of the whole soul in righteousness and true holiness, it is not a matter that may be disregarded; heaven is a place of holiness, and nothing but what is like itself can ever enter into it.

4 Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?

[How can a man be born when he is old?] Nicodemus here struggles to reconcile what he has just heard with his own observations of life.

5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
7 Marvel not that I said unto thee, Ye must be born again.

[That which is born of the flesh is flesh] The answer to Nicodemus' question. Even if it were possible to repeat physical birth the result would be the same. The plant will ever be of the nature of the seed which begets it - like will beget like. The kingdom of God is spiritual and holy; that which is born of the Spirit resembles the Spirit; for as he is who begat, so is he who is begotten of him. Therefore spiritual regeneration is a necessity to prepare the soul for a holy and spiritual kingdom.

8 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.

[The wind bloweth] Though the manner in which this new birth is effected by the Divine Spirit be incomprehensible to us, yet we must not, on this ground, suppose it to be impossible. The wind blows in a variety of directions - we hear its sound, perceive its operation in the movement of trees and feel it on ourslves, but we cannot discern the air itself. So is every one who is born of the Spirit; the efects are discernable and as sensible as those of the wind; but itslf we cannot see. But he who is born of God knows that he is thus born. The spirit itself, the grand agent in this new birth, bears witness with his spirit that he is born of God, Romans 8:16, for he that believeth hath the witness in himself, 1 John 4:13 and 5:10 and Galatians 4:6. So does this spirit work in and by him that others, though they see not the principle, can easily discern the change produced.

[How can these things be?] Our Lord had very plainly told him how these things could be, and illustrated the new birth by one of the most proper similes that could be chosen, but the natural man, Nicodemus, was accustomed to making everything submit to his natural senses and found it difficult to accept that which he could not comprehend. A not uncommon reaction today.

10 Jesus answered and said unto him, Art thou a master of Israel, and knowest not these things?

[Art thou a master of Israel...?] Have you taken it upon yourself to guide the blind into the way of truth and yet do you not know that truth yourself? This was no surprise to Jesus but he wished to make the point with Nicodemus.

11 Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness.
12 If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?

[We speak what we do know] I and my disciples do not profess to teach a religion which we do not understand, nor exemplify in our conduct. A strong but very delicate reproof to Nicodemus, who, though a master of Israel, did not understand the rudiments of the doctrine of Salvation.

[Ye receive not our witness.] It was deemed criminal among the Jews to question or depart from the authority of their teachers. Nicodemus grants that our Lord is a teacher come from God, yet hesitates to receive his testimony relative to the new birth and the spiritual nature of the Messiah's kingdom.

13 And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven.

[No man hath ascended up to heaven] Our Lord probably spoke to correct a false notion among the Jews; that Moses ascended up into heaven to get the law. It is not Moses who is to be heard now, but Jesus. Moses did not ascend to heaven, but the Son of Man is come down from heaven to reveal the Divine will.

[He that came down from heaven] The incarnation of Christ is represented here under the notion of his coming down from heaven to dwell on earth.

14 And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:

[As Moses lifted up] He shows the reason why he descended from heaven, that he might be lifted up, i.e. crucified, for the salvation of mankind, and be, by the appointment of God, as certain a remedy for sinful souls as the brazen serpent elevated on a pole (Numbers 21:9) was for the bodies of Israelites who had been bitten by the fiery serpents in the wilderness.

15 That whosoever believeth in him should not perish, but have eternal life.

[That whosoever believeth] These words contain the reason for the subject of the following verse.

16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.

[For God so loved the world] Such a love as that which induced God to give his only begotten Son to die for the world could not be described - Jesus Christ does not attempt it. He has put an eternity of meaning in the particle so, and left a subject for everlasting contemplation, wonder and praise, to angels and men. From the subject before him, let the reader notice the following points.
First, the world was in a ruinous, condemned state, about to perish everlastingly, and was utterly without power to rescue itself from destruction.
Secondly, That God, through the impulse of his eternal love, provided for its rescue and salvation, by giving his Son to die for it.
Thirdly, That the sacrifice of Jesus was the only means by which the redemption of man could be effected, and that it is absolutely sufficient to accomplish this gracious design.
Fourthly, that sin must be an indescribable evil when it required no less a sacrifice, to make atonement for it, than God manifested in the flesh.
Fifthly, that while this sacrifice was for all, no man is saved but he that believes, i.e. believes what God has spoken concerning Christ, his sacrifice, the end for which it was offered and the way in which it is to be applied.
[There is a difference between mere intellectual acknowledgement and saving belief. When I was a child and left uneaten food on my plate my father would sometimes reprove me with, "There are starving children in Africa who could live for a day on what you have wasted." I believed my father but it did not move me much. Had I been one of those starving children and been offered that plate of food my reaction would have been to happily accept it, thinking, "How wonderful! I need this food and here it is, for ME."]
Sixthly, Those that believe receive double benefit; 1. They are exempted from eternal perdition - not perish. 2. they are brought to eternal glory - everlasting life.

17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.

[For God sent not...] It was the opinion of the Jews that the Gentiles, whom they often term the world, were to be destroyed in the days of the Messiah. Christ corrects this false opinion; and teaches here a contrary doctrine. God, by giving his Son and publishing his design in giving him, shows that he purposes the salvation, not destruction, of the world, the Gentile people. Nevertheless, those who will not receive the salvation he has provided for them, whether Jews or Gentiles, must necessarily perish.