9 How can this be? Nicodemus asked.
10 You are Israels teacher, said Jesus, and do you not understand these things? 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. 12 I have spoken to you of earthly things and you do not believe; how then will you believe if I speak of heavenly things? 13 No one has ever gone into heaven except the one who came from heaventhe Son of Man. 14 Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, 15 that everyone who believes may have eternal life in him.
Given this background information Christ tells Nicodemus something that He knows that Nicodemus has not been taught. Giving the implication the teaching is not new, as per the question of Nicodemus “Art thou a master of Israel, and knowest not these things?.....”
I have no clue who is the first one that decided they would fix the Words Christ spoke to Nicodemus, but the words ‘born again’ are not the words or the message or the instruction Christ was giving to Nicodemus or to Christians.
Christ is telling any and all the first requirement to SEE the kingdom of God... Except a man/woman be born *from above*, he/she cannot SEE the kingdom of God.
Those of Genesis 6 and Jude refused to be born of woman and journey through this flesh age, and they have already been sentenced to death. But, that sentence has yet to be fulfilled.