As I've been preparing to preach this coming Sunday on John 3, something extremely important comes to mind. This text is very clear that no one can see the kingdom unless they are first born again, and that the only way one is born again is through the Spirit who goes wherever He wills. In The Pillar New Testament Commentary for John, D. A. Carson says of verse 8:
"The point is that the wind can be neither controlled nor understood by human beings (remembering of course that this was written before modern meteorology alleviated at least some of our lack of understanding). But that does not mean we cannot detect the wind's effects. We hear its sound, watch the swaying grasses, see the clouds scudding by, hide in fear before the worst wind storms. So it is with the Spirit. We can neither control him nor understand him. But that does not mean we cannot witness his effects. Where the Spirit works, the effects are undeniable and unmistakeable." (Page 197)
Isn 't it great to know that even though He goes where He wills, we can still see His work when someone is born-again?