John 3:3 – “Jesus answered and said to him, “Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God.“
In other words: Unless you are born again and receive the right instruction, you are wandering somewhere out there far away from the kingdom of heaven. But he does not speak as plainly as this, preferring to make what he says easier to hear by generalizing, “Unless one is born again.” In this way he does not specifically address his remarks at Nicodemus.… Now, if he had spoken to the Jews this way they would have ridiculed him and then left. But Nicodemus shows he wants to learn.… And so what Christ says to him is something like this: If you are not born again, if you do not share in the Spirit that comes through the washing of regeneration, everything you think about me will be from a human point of view, not a spiritual one.… Now, some take the expression “again” [Greek: anōthen (“again” or “from above”).] to mean “from heaven”; others think it means “from the beginning.” Either way, it is impossible, Christ says, for someone who is not born in this way to see the kingdom of God. By these words our Lord discloses his nature, showing that he is more than what he appears to the outward eye.
John Chrysostom (349AD-407AD),
Early Church Father,
From “Homily 24 on the Gospel of John”