Nicodemus was drawn to Christ, but ashamed to be seen with him, so he approached him at night. Yet Jesus welcomed him, and taught him. Early in our faith we are uncommitted and unsteady, but we learn to proclaim Jesus boldly. Nicodemus posed no question, but Jesus provided the answer, because he knows what we seek. We must be repentant and accept Christ to enter the kingdom of heaven. We must transformed into holiness by the Spirit of God. We cannot attempt to put a man made explanation onto the workings of the God, it is like trying to see the wind. We can only know the wind is there by witnessing the changes in makes in its environment- how the tree branches move, how it cools or warms, and how we sense it around us. For those who have never felt or percieved God moving in their life, this can be a difficult concept. We should witness to the movement of God in our lives, and testify how he changes us. Jesus mentions how he and his disciples have been preaching, and yet the Pharisees did not believe. We are faced with this issue in our lives. When we are not believed, we feel discouraged. We have to remember that Jesus was not believed either, and He was the Son of God! The Son of God knows how you feel.
Nicodemus, a teacher and man of God, struggled to grasp the concept of purifying his heart! No doubt he was a learned man, and had studied the Word of God, yet even he was confused. This illustrates the issue Jesus addresses about the Pharisees, and this is why our one teacher is Jesus, as men are fallible.
When poisonous snakes plagued the Israelites, Moses was instructed to raise a serpent statue, that whoever looked on it after being bitten would live. Jesus refers to himself in this way- that the people who are plaugued and poisoned by sin must seek him, as he was raised on the cross, and then raised from the dead, for our salvation.
God permitted all this because He loves us. Jesus witnessed here of the mercy, love, and goodness of God. God did not seek to destroy the world, but to save it. He sent us Jesus for this reason. Those who commit sin willingly without repentance despise the truth; they do not want to be told they are sinning. But those that come to Jesus welcome the truth, and allow the spirit to tranform them. Jesus promises eternal life to all who believe in him, because God loves us.