Born 'Again' Defined

What exactly does it mean for one to be "born 'again"? The word "again" has a specific meaning.

Since words mean something, it is obvious that only one who has been born of God's doing a 'first time' can be 'born again.'

You will recall that Abraham and his wife Sarah, who was "dead in here womb" miraculously had a son who was promised by the Lord and through the Lord's intervention. She conceived and bore a "son of promise," Isaac.