Nicodemus first came to Jesus by night. So he is identified as the man who came to Jesus by night. But his conversation with Jesus reveals that he is a sincere admirer of Jesus and a true Seeker of Truth. His name in Greek mean Victor over the people.
Only John speaks about Nicodemus in the New Testament. In Johns Gospel Nicodemus appears on three occasions.
In the beginning of chapter 3 John describes him: There was a Jewish leader named Nicodemus, who belonged to the party of the Pharisees. One night he went to Jesus and said to him, Rabbi, we know that you are a teacher sent by God. No one could perform the miracles you are doing unless God were with him (Jn 3, 1-2).
Nicodemuss words to Jesus reveals much about the person. He is a Pharisee; that means a leader of the Jewish people and a member of Sanhedrin the great and powerful Jewish Council.
In his first meeting with Jesus he recognizes Jesus as Rabbi which means a much-respected Teacher. Rabbi is the title given always to Jesus in New Testament.
By saying, You are a teacher sent by God, Nicodemus reveals that he must have known about Jesus before. He may be meeting Jesus first time that night. But he has heard much about the itinerant preacher that Jesus was. Nicodemus must have heard about his miracles. He must have known about Jesus encounter with other Pharisees and Sadducees. He must have learnt about Jesus teaching and his parables.
From his knowledge of Jesus, Nicodemus has concluded that Jesus was a man of God; he has come from God. So Nicodemus acknowledges Jesus as one who lives in the presence of God.
In their first encounter Jesus tells Nicodemus that, Very truly, I am telling you the truth: no one can see the Kingdom of God unless he is born again (Jn 3, 3). But Nicodemus does not grasp exactly what Jesus is telling him.
So he humbly asked Jesus, How can a grown man be born again? (Jn 3, 4).
Jesus explains to him about being born of water and spirit. Even such teaching of Jesus is beyond Nicodemus understanding. So he asks Jesus again, how can these things be? This time Jesus is surprised by Nicodemus query and tells him, You are a great teacher in Israel, and you dont know this? (Jn 3, 10).
Anyway, Jesus explains Nicodemus patiently till he understood him well. This first meeting with Jesus must have left a deep and lasting impression on Nicodemus. This is seen from the fact that he spoke for Christ in the second occasion who John presents him in his Gospel.
Towards the end of Jesus ministry the admiration of the people in Jerusalem for Jesus steadily grew and they began to recognize him saying This man is really the Prophet and This is the Messiah (Jn 7, 40-41). Then, the Chief Priests and Pharisees got panicky about Jesus popularity. So they send the temple police to arrest him. But they did not dare to arrest Jesus because, as they reported, Never has anyone spoken like this!
Nicodemus admiration for Jesus is seen when he appears in the third time in Johns Gospel even after the death of Jesus. This is how John narrates the event. When Jesus died on the cross, After this, Joseph, who was from the town of Arimathea, asked Pilate if he could take Jesus body. (Joseph was a follower of Jesus, but in secret, because he was afraid of the Jewish authorities.) Pilate told him he could have the body, so Joseph went and took it away.
Nicodemus, who at first had gone to see Jesus at night, went with Joseph, taking with him about thirty kilogrammes of spices, a mixture of myrrh and aloes. The two men took Jesus body and wrapped it in linen with the spices according to the Jewish custom of preparing a body for burial. There was a garden in the place where Jesus had been put to death, and in it there was a new tomb where no one had ever been buried. Since it was the day before the Sabbath and because the tomb was close by, they placed Jesus body there (Jn 19, 38-42).
When most disciples have ran away at the arrest and death of Jesus on the cross, Nicodemus comes openly rendering loving service to the death body of Jesus and helps Joseph of Arimathea, another secret admirer of Jesus. They both assure a decent burial for Jesus.
We do not get much information about discipleship of Nicodemus in the Gospel. But many traditions credit Nicodemus becoming a faithful follower of Jesus in later years.