Nicodemus was an important religious leader who thought that he knew everything about getting to heaven, but Jesus had to shake him out of being reliant on himself. Nicodemus would say: 'Learn God's law and work hard at obeying it.' Jesus was saying 'No, no Nicodemus, you will not get to heaven with your own strength because human life can only reproduce human life, but the Spirit of God reproduces a spiritual life. So, you need to look to God to save you.'