New International Version John 3:
1Now there was a Pharisee, a man named Nicodemus who was a member of the Jewish ruling council. 2He came to Jesus at night and said, “Rabbi, we know that you are a teacher who has come from God. For no one could perform the signs you are doing if God were not with him.”
Unlike some other Pharisees, Sadducees, and teachers of the law, Nicodemus was being humble in meeting Jesus.
3Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again. ”
Jesus introduced the concept of born-again. Naturally, Nicodemus wondered what it was about and asked an innocent question.
4 “How can someone be born when they are old?” Nicodemus asked. “Surely they cannot enter a second time into their mother’s womb to be born!”
5 Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit. 6Flesh gives birth to flesh, but the Spirit b gives birth to spirit. 7You should not be surprised at my saying, ‘You must be born again.’ 8The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit.”
After hearing Jesus' answer, Nicodemus still had trouble understanding the concept and followed up with a further innocent question.
9 “How can this be?” Nicodemus asked.
Nicodemus did not contradict Jesus. He seemed sincere in his questions. Uncharacteristically, Jesus did not respond graciously.
10 “You are Israel’s teacher,” said Jesus, “and do you not understand these things?
You are Israel’s teacher. You should have known.
11 Very truly I tell you, we speak of what we know, and we testify to what we have seen, but still you people do not accept our testimony. 12I have spoken to you of earthly things and you do not believe;
Nicodemus had not expressed unbelief as a spoken statement of fact. He merely raised questions, trying to understand what Jesus said. Jesus was more gracious in his encounter with e.g., the Samaritan woman at the well. Why didn't Jesus elaborate on his answer so that Nicodemus could understand born-again better? In fact, the elaboration would have benefited us.
Related questions:
What was Nicodemus supposed to know from the Old Testament about being born again?
Does the idea of being "born again" have a root earlier than John/Peter (or Jesus)?
My question is more about Jesus' mindset and less about Nicodemus'. Sure, Nicodemus should have known if he were smart and objective. Still, why was Jesus being harsh to his innocent questioning? Nicodemus wasn't being stubborn like other Pharisees. He did believe later.