In the third chapter of the gospel of John we meet Nicodemus. Nicodemus was "ruler of the Jews." He was a notable Pharisee and perhaps even a member of the Sanhedrin. He came to Jesus to find out if He was really from God. He had heard of the many miracles wrought by Jesus and wondered if such could be performed by someone not sent of God.
It was not unusual for Pharisees and Scribes to follow Jesus around, but they did so in an attempt to trip Him up and discredit Him. This was not Nicodemus's reason for approaching Jesus however, so he did so in secret, coming to Jesus at night.
Perhaps Nicodemus feared criticism from the Jews, After all the Scribes and the Pharisees were against Jesus. Surely, if Nicodemus were not trying to discredit Jesus he would be criticized by the other Temple leaders. Or it might be that Nicodemus wanted uninterrupted conversation with Jesus. During the daytime hours Jesus was inundated by throngs of people, but at night he might have opportunity to get Jesus alone. Another possibility for Nicodemus's night visit to Jesus is that he was conducting a private investigation before offering his opinion publicly. Whatever the reasons, Nicodemus came at night and asked Jesus,
"Rabbi, we know that You have come from God as a teacher; for no one can do these signs that You do unless God is with him."
Jesus does not give an opinion of Nicodemus's words. He does not respond to it at all. Instead He addresses Nicodemus's immediate need. Even though Nicodemus was a ruler of the Jews he was spiritually dead. Jesus knew what Nicodemus needed and he addressed that issue instead of Nicodemus's words,
"Truly, truly, I say to you, unless one is born again, he cannot see the kingdom of God."
Now this statement must have confused Nicodemus just a bit! Born again? That's going to be a little difficult, don't you think? So Nicodemus says that to Jesus, "How can a man be born when he is old? He cannot enter a second time into his mother's womb and be born, can he?" That was Nicodemus's what of saying, "What the heck are you talking about?"
So Jesus explains that in order enter the kingdom of God one must be born of both water and the Spirit. "Do not marvel that I said to you, 'You must be born again.'"