Why did Nicodemus come "by night" (John 3:2)?
Nicodemus most likely didn’t want to be seen.
Nicodemus was one of the nation's top religious-political leaders, and being seen with, let alone going to see a new street preacher who was doing and saying some unorthodox things may not have been the best thing for his reputation.
How would you characterize Nicodemus' opening line?
It sounds pretty gracious and respectful. He calls Jesus not only a "teacher" but one "from God" (John 3:2).
Is Nicodemus' opening line correct?
Not quite. Jesus IS God, not a teacher from God.
How might Nicodemus have expected Jesus to reply?
Given the disparity in their relative social status, Nicodemus may have expected Jesus to show some appreciation for the compliments.
Does Jesus live up to his expectations?
What is Jesus saying?
Look, you have no clue because you haven’t been "born again" (John 3:3).
What does it mean to be "born again"?
The original Greek word translated "again" more commonly means, "from above" often implying heaven. This Greek word occurs 13 times in the Bible, and is translated “from above” 5 times, “top” 3 times, “again” twice, “from the first” once, “from the beginning” once, and not translated once. Jesus is saying that Nicodemus "cannot see the kingdom of God" (John 3:3) until he has been born spiritually.
What do you think of Nicodemus' reply?
If Nicodemus had stopped with just the first question, "How can a man be born when he is old?" (John 3:4), he would have just expressed incomprehension. But with his second question, "Can he enter a second time into his mother’s womb and be born?" (John 3:4), he may have been either trying to make light of Jesus’ reply, which he may consider to be a snub in front of those around, or express shock since being born a Jew was what the Jews counted on as guaranty of automatic access to heaven