Nicodemus - in spite of the fact that he was a Pharisee, leader of the Jews (Sanhedrin: the highest governing body of the Jews), a person of wealth, influence, and teacher of the Law, he could not “see the Kingdom of God” without being born again. For even a man of such prestige and stature, still needed salvation from above. He should have been familiar with Ezekiel and other OT Scriptures, revealing the spiritual truth of this new birth. As a Pharisee he probably had too much confidence in his own righteousness and had not welcomed the humble thought of repentance, the need to have his life cleansed and his heart transformed.
"If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?" - JESUS