Nicodemus was a Pharisee, a member of the ruling council, and a respected teacher of Israel. He came to Jesus at night and called Him a teacher come from God. Jesus went straight to his deepest need. Unless one is born anew, he can't see God's Kingdom. Nicodemus thought of physical birth, but Jesus meant a spiritual birth. We need a new heart, washed clean and made alive by the Spirit, as the prophet Ezekiel had promised.
Jesus compared the Spirit to the wind. It blows where it wants. We see its effects, though we cannot control it. Then Jesus explained how this new life comes. In Numbers 21, God told Moses to lift up a bronze serpent, and those who looked at it lived. Even so, the Son of Man must be lifted up on the cross, that whoever believes in him should not perish, but have eternal life.
The best-known verse in the Bible follows. God so loved the world that He gave His one and only Son. God's love is the reason for the gift, the world is the object, and eternal life is the result. God sent His Son to save, not to condemn. Yet light exposes darkness, and some people love darkness because their deeds are evil. Meanwhile, John the Baptist's disciples worried that people were leaving John for Jesus. John answered with joy, He must increase, but I must decrease.