You can't work your way to heaven.

Forgiveness of sins and a relationship with God is something that can not be earned. It is what God gives freely to those who seek him with a pure heart.

The Passover is a religious holiday that God instituted with the nation Israel. The nation of Israel took the religious ceremony and turned it into a way for man to try and earn or buy God's favor. Jesus, I think, started to show the Jews that the religious system of that time was not what God had intended. He threw the individuals who had turned the worship systems that God had implemented into money making schemes, out of the Temple. His anger was prophesied in Psalm 36:9, and when the Jews remembered the prophesy they asked Jesus to show them a sign to prove He was God. He answered them and said" Destroy this temple and in three days I will raise it up. They couldn't believe Him because it had taken man forty-six years to build the temple. They did not understand that He was speaking of His body.

Jesus goes on to meet with Nicodemus, a teacher of the Jews. In the conversation Jesus explains to him that a man must be born again to see the things of heaven. That second birth is of the spirit. The first is natural, of the water. Nicodemus showed that he did not understand by asking if a man must enter his mother again and be born again. I believe he was seeking man's way to enter heaven. God's way involved a spiritual work of God. That way includes mans belief in God's Son, Jesus, and the work that God does through Jesus. The Spirit of God does a supernatural work in the heart of man to give him an understanding of the spiritual things of God. Belief springs forth from the work of God. God will reveal Himself to those who diligently seek Him.