The wind{The same Greek word (pneuma) means wind, breath, and spirit.} blows where it wants to, and you hear its sound, but don't know where it comes from and where it is going. So is everyone who is born of the Spirit."
This is pretty much what Jesus said to Nicodemus. "No man has descended into heaven but he which came down from heaven, even the Son of man which was in heaven. And I've told you earthly things and you believe not. How would you believe if I've told you of heavenly things?" So, he speaks of Jesus coming down from heaven, but no man receiving His testimony.