The world that we live in demands that there be covenants and agreements that bind two parties together in a mutually beneficial relationship. The problem is that we often take this world for ultimate reality. The gospel will not allow us to do so. In the story of Nicodemus we have a man, a great leader of the people, who comes to Jesus by night. Now the fact that Nicodemus comes at night is very significant in the Gospel of John.
Darkness carries powerful symbolic weight.
Darkness is that which opposes the light of God's revelation in Jesus. The light shines in the darkness, and the darkness did not overcome it. Now Nicodemus comes under cover of darkness. Perhaps he fears that others might catch him with Jesus. But Jesus does not become anxious but uses the opportunity to teach.