When Jesus is teaching Nicodemus about the absolute necessity of the new birth, Nicodemus does not understand what He is talking about. In response to that bafflement, Jesus says this:
If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things (John 3:12)?
Catch that? Being born again is not about “heavenly things.” It is not the creation of heavenly ambrosia for us to sip during the remaining days of our earthly toil. It is the creation of earthly wine from earthly water.
Heaven acts when a man is born again, but heaven is not transferred. It was supernatural power that Jesus exercised when He turned water to wine, but the result was not supernatural wine.
Jesus indicates to Nicodemus that there are heavenly doctrines that would stagger him, but we can’t go there until the earthly a,b,c’s are mastered first. He was having trouble in the earthly kindergarten, and so we have to postpone the heavenly graduate school.
So regeneration is not an esoteric doctrine. It is not something we are allowed to postpone discussion of until later. It is the sine qua non of being able to discuss anything later. If a man is not born again, he will not be able to see the kingdom, much sit down in that kingdom to learn the things that Jesus said were so far beyond us now.
This is because when we are born again, a dramatic miracle happens. When we are born again, we are turned into people.