John 3:6

That which is born of the flesh - To show the necessity of this change, the Saviour directs the attention of Nicodemus to the natural condition of man. By “that which is born of the flesh” he evidently intends man as he is by nature, in the circumstances of his natural birth. Perhaps, also, he alludes to the question asked by Nicodemus, whether a man could be born when he was old? Jesus tells him that if this could be, it would not answer any valuable purpose; he would still have the same propensities and passions. Another change was therefore indispensable.

Is flesh - Partakes of the nature of the parent. Compare Genesis 5:3. As the parents are corrupt and sinful, so will be their descendants. See Job 14:4. And as the parents are wholly corrupt by nature, so their children will be the same. The word “flesh” here is used as meaning “corrupt, defiled, sinful.” The “flesh” in the Scriptures is often used to denote the sinful propensities and passions of our nature, as those propensities are supposed to have their seat in the animal nature. “The works of the flesh are manifest, which are these: adultery, fornication, uncleanness, lasciviousness,” etc., Galatians 5:19. See also Eph 2:3; 1 Peter 3:21; 1 Peter 2:18; 1 John 2:16; Romans 8:5.

Is born of the Spirit - Of the Spirit of God, or by the agency of the Holy Spirit.

Is spirit - Is spiritual, “like” the spirit, that is, holy, pure. Here we learn:

1.That all men are by nature sinful.

2.That none are renewed but by the Spirit of God. If man did the work himself, it would he still carnal and impure.

3.That the effect of the new birth is to make men holy.

4.And, that no man can have evidence that he is born again who is not holy, and just in proportion as he becomes pure in his life will be the evidence that he is born of the Spirit.