For the proclamation of the Gospel and the edification of the Body of Christ
When the Lord Jesus tells Nicodemus that he must be born again, he is using a Greek word that can also be translated as "from above". In fact, some Bibles use it that way, but Nicodemus understood the simpler meaning that fit into his own system of beliefs.
According to him, a gentile had to experience the luck of regeneration if he wanted to be part of Gods people, but never a Jew like him. Therefore, he was thinking in a physical birth, and so his surprise and question follow: "How can a man be born when he is old?".
But the Lord was referring to a heavenly birth. The Greek word "anöthen" is translated as "from heaven" in John 3:31 (Spanish Version); and as "from above" in John 19:11. This is how the birth from above is established as an essential requirement to enter into Gods kingdom. In the first chapter of John it has already been said: "But as many as received Him, to them He gave the right to become children of God, to those who believe in His name who were born, not of blood, not of the will of the flesh, nor of the will of man, but of God" (John 1:12-13).
In the gospel of John there is a great difference between what is earthly and heavenly. John the Baptist says: "A man can receive nothing unless it has been given to him from heaven" (John 3:27); and then he adds: "He who comes from above is above all he who comes from heaven is above all" (3:31), in reference to our Lord Jesus.
Nicodemus was a good and pious man; upright according to the law. But the words of the Lord clearly tell us that it was not enough for Nicodemus to be perfected according to the law, but that he needed divine intervention, a birth from above. Even the best natural man is infinitely inferior than the worst spiritual man. The most select human manufacture is nothing before the glory of that which is born from heaven.
That is why the Lord chose Nicodemus to tell him this. He could have said this to the Samaritan woman, or to the man who was born blind, but he did not. He tells this to the best of men, so that we will not think that it is enough to have a perfected human nature, or a man trained in certain virtues.
Nicodemus, like all men, belongs to Adams lineage, and this lineage is irremediably lost. A new nature needs to be introduced in us if we want to enter into Gods territory; a nature that resists time and eternity. "All flesh is as grass and all the glory of man as the flower of the grass; the grass withers, and its flower falls away", says the prophet.
Only what comes from above will remain standing when this earth and sky are removed. Only what is born from above will remain forever.