From among the crowds appeared one called Nicodemus, he was deeply pious and prominent, one of the seventy in the Sanhedrin. He recognized the power of God active in Christ. Perhaps he wished to build a bridge between this new prophet and the Jewish assembly. At the same time he feared the high priest and the common folk. He was uncertain about the person of Jesus. He came to Jesus secretly in the dark, wishing to test Jesus before joining his circle.
By ascribing the title "teacher", Nicodemus was expressing a majority view, who saw Christ as one who taught the Scripture with a band of followers. He agreed that Jesus was sent from God, attested by signs. He confessed, "We believe that God is with you and upholds you. You may be the Messiah?" This was more an implicit admission.
Jesus answered his question, not entirely relying on this go-between from the leaders of the people to Christ. He saw Nicodemus’ straying heart, his sins and his longing for righteousness. He could help him only after showing up his spiritual blindness. Despite Nicodemus’ piety, he did not truly know God. Jesus was frank with him and said, "Surely no man can know God by his own efforts; he needs the regeneration of the heavenly Spirit."
This pronouncement was Christ’s judgment on theological studies and dogmas based on logic alone. For knowledge of God comes not by intellectual lectures, but by new birth. On a radio set, unlike a TV, you can turn knobs as you please, but you cannot get any images. Pictures require a set that is totally different from the radio. So also the natural man, despite his piety and activity, cannot see God, not by thought or feeling. This spiritual realization requires a revolution, a heavenly birth and a new creature.