Rebirth = Inward Circumcision + Outward Circumcision
The Gospel of John was written by John in about 100AD to clear up some issues for the Church. John was the last disciple to die.
John is the only Gospel that mentions the term 'Born Again'. He says that nobody can enter the kingdom of God unless they are Born Again.
To be Born Again, you must be Born of Water and Born of the Spirit.
Why is it that none of the other Gospels mention the term Born Again?
If Born Again is such an important thing, then how come Matthew, Mark and Luke do not mention it?
The answer is that Regeneration (Born Again) is the same as Baptism in the Spirit.
Baptism in the Spirit is mentioned at the beginning of every Gospel. John came to baptize with Water for repentance but Jesus came to Baptize with the Holy Spirit and Fire.
Baptism in the Spirit and Regeneration are the beginning of our walk with Jesus. They are the same as 'Receiving the Spirit' which is how we become a 'Child of God'.
We are all baptized into the Body of Christ by one Spirit.
This explains why Matthew, Mark and Luke do not use the term Born Again, as it is the same as Baptism in the Spirit which happens at Conversion when we believe and accept Jesus as Lord.
Why then do we need the term 'Born Again' if it is the same as Baptism in the Spirit?
Jesus first used the term 'Born Again' when he was visited by Nicodemus. Nicodemus was a leader of the Pharisees, a member of the Sanhedrin; a teacher of Israel.
The Jews were God's Chosen People and Jesus was a Jew himself. The Jews had an eternal covenant with God symbolized by circumcision. Circumcision was not just outward; it was necessary to be circumcised inwardly by the Spirit (circumcision of the heart by the Spirit) in order to be a Jew.
Nicodemus recognised that Jesus had come from God. Jesus said that nobody could even see the Kingdom of God unless they are Born Again. Nicodemus asked how an old person could be Born Again to which Jesus replied that nobody can enter the Kingdom of God unless they are Born of water and the Spirit. The wind blows where it wills; so it is with everybody who is Born of the Spirit. Jesus said "You are Israel's teacher and yet you do not know all these things!!".
Jesus expected Nicodemus to know all about Spiritual rebirth as it was just as intrinsic to the teachings of the Old Testament as the New Testament.
Jesus was introducing the term Born again to refer to all who a spiritually regenerated whether it is under the Old or the New Covenant.
The term 'Born Again', therefore, refers to both Baptism in the Spirit and Circumcision by the Spirit.
Now, the only way to be Born Again is by Baptism in the Spirit.
Jesus is the one who Baptizes with the Spirit when he feels we are good and ready.
Many different terms for Regeneration
God people could have been Born of Water
in a number of different ways
The Term 'Born Again' includes all the Children of God in the Old and the New Testament