There was a man from the Pharisees who was called Nicodemus, a principal among the Jews. He came to Jesus at night and told him; Rabi, we know that you have come from God as a teacher; because no one can make these signs that you do if God is not with him. Jesus answered and said: Verily, verily, I say to you, he who is not born again cannot see the kingdom of God. (version QUEEN VALERA 1960)
A very interesting topic is that this Pharisee seems to have been sent to try to convince Jesus that they were well and that everything was fine and that they did not need anything else to please God.
Jesus attacked the root of the problem and told him that he must be born again to see the kingdom of God, and that is that they believed themselves with moral superiority before all the others and that they did not need to repent of anything, Jesus knew it and knew the intentions of this man.
Although it is a well-known verdict, not everyone knows the true meaning and that being born again represents believing in Jesus and dying the old man because of this, Paul said, I no longer live if Christ lives in me. It is to stop living one to live by the Holy Spirit of God.