What does John 3:9 mean?

Nicodemus is a Pharisee, and a member of the Sanhedrin court. This means he is well educated, intelligent, and very interested in moral behavior. He knows the law of Moses, and the rest of the Hebrew Scriptures very well. At the same time, Nicodemus came to Jesus looking for answers. In verse 2, he indicated that seeing miracles is what led him to believe Jesus was from God. However, as a Pharisee, his perspective is very legalistic. From Nicodemus' point of view, what Jesus is saying about "the flesh" and "the Spirit," or about being "born again" is completely upside down. What Nicodemus needs to realize is that knowledge and moral behavior aren't enough to make him right with God. As long as he thinks that he can make things right by himself, he's going to be lost. So, Jesus (lovingly) takes him down a notch or two. In verse 10, Jesus points out that even though Nicodemus is a "teacher" of Israel, his knowledge is clearly incomplete.