John 3:5–6

"That which is born of the flesh is flesh" — a very solemn truth about what man is, as man. Everything shares the moral character of its source. Flesh is flesh. Do what you like with it, it is flesh, and nothing but flesh. Educate it as far as you can, and it is still flesh, not spirit... You may refine the flesh as you like, but you will never distil spirit out of it. "That which is born of the Spirit is spirit." It takes after its source; its nature is the same as its source.

The Apostle John goes to the very root of things — nature — when he says, "That which is born of the flesh is flesh" (John 3:6). Here "flesh" means the fallen sinful nature of man. "Flesh" in Scripture sometimes means the physical body, such as "flesh and bones." Used that way, it includes the Lord Himself. But mostly the word refers to our fallen sinful nature. In that nature the blessed Lord had no part, or else He would be one of us and no Saviour.

Nicodemus comes and applies to Him as a teacher. No, no, says the Lord, I am not going to teach flesh, Nicodemus; it is not a question of teaching yet. You must get another life first; you must be born again; you do not need teaching until you have life... Flesh never ceases to be flesh. I must be born of the Spirit, a partaker of the divine nature, born of God.

Nicodemus is the only person to whom the Lord spoke of the absolute necessity of the new birth. He never made such a statement to the tax collectors and the prostitutes. And who was Nicodemus? A Pharisee, and therefore an extremely religious man. A ruler of the Jews, which required a moral life. The teacher of Israel, a man of much learning. Religion, morality, education and culture are not enough. They cannot save a man or give him a place in the Kingdom of God... The new birth is not reformation. Nor is it, as people often say, an action of the Holy Spirit to make an evil nature good. Nothing can change the flesh into something better. In the new birth the Holy Spirit imparts a new nature, the divine nature.

Human nature can never be refined. It can never be improved or changed enough to rise up into any acquaintance with the things of God. No spiritual process whatever can turn it into divine nature. On the other hand, the new nature does not decay. It can never be reduced to "the flesh," or to the nature of man as he is. Our Lord says on the one hand, "That which is born of the flesh is flesh." On the other hand He says, "that which is born of the Spirit is spirit." It takes the character of its source.

Thank God, the believer in the Lord Jesus has a new nature — a nature that is at home in the presence of God — a nature that loves holiness and shrinks from evil... Scripture says of the one born of God that he cannot sin. That is a strong statement, but the inspired writer is looking at the believer in the abstract, as identified only with the divine nature. Just as you might say that a vine cannot bear thorns, or a fig tree thistles, but only the fruit that expresses its nature, so it is with the divine nature — it must express itself; it cannot sin.

New birth comes from the Holy Spirit, and the result, as John 3:6 shows, is a new nature which is "spirit" in its essential character. What the Spirit produces shares His own nature. Keep this distinct from the Holy Spirit living in someone already born again.