Now there was a Pharisee, a man named Nicodemus who was a member of the Jewish ruling council. He came to Jesus at night and said, “Rabbi, we know that you are a teacher who has come from God. For no one could perform the signsyou are doing if God were not with him.” Jesus replied,
“Very truly I tell you, no one can see the kingdom of God unless they are born again.”
“How can someone be born when they are old?” Nicodemus asked. “Surely they cannot enter a second time into their mother’s womb to be born!” Jesus answered,
“Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit. Flesh gives birth to flesh, but the Spirit gives birth to spirit. You should not be surprised at my saying, ‘You must be born again.’ The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit.”
The very first thing Jesus tells Nicodemus at their meeting is that he must be born again. This may seem to come completely out of left field, but let's look more closely at what Jesus is saying. In his next response, Jesus explains to Nicodemus that he is discussing baptism - in water and from the Holy Spirit. And he also says that the Spirit is key to seeing God's kingdom. Therefore, in his first sentence Jesus is trying to tell Nicodemus, "Look, nothing I say will make sense to you unless you have the Holy Spirit living in your heart. I AM the kingdom of God coming to this earth; you can't speak my language unless you let God put his Spirit in your heart." Finally, Jesus tries to use an analogy of how the Holy Spirit is like the wind. Our Counselor lives in our hearts giving us God's wisdom and the strength we need to get through each day (we can "hear" the Holy Spirit's sound/voice), but we can never fully know God's all-encompassing and perfect plan for the world (where the Spirit "comes from" or "is going"). For that, we will just have to wait until Jesus comes again.
(Start at the beginning HERE.)