1 Corinthians 15: 49: And as we have borne the image of the earthy, we shall also bear the image of the heavenly.
Jesus was the first person to be born again. We know this to be true because before His incarnation into flesh, He was the Son of God or the Logos (the Word [John 1: 1]) that came out of God. John 3: 16 then tell us: For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. Begotten means to be born, so when Jesus was born in Bethlehem, this was not actually His first birth, but was in fact His second birth, for He had already been begotten way back in Eternity as the first visible thing (the Son of God as the Pillar of Fire) to come out of the invisible Spirit of Elohim.
Jesus’ second birth was His incarnation into flesh by His nativity in Bethlehem; so then the second birth for a Christian is also connected to incarnation. Jesus said to Nicodemus in John 3: 3: Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God. Jesus, who was first born of the Spirit from Heaven, was then born again of the flesh on earth, so that we who were first born in the flesh by sin on the earth could be born again of the Spirit from Heaven. Furthermore, Jesus who was first born of God, was then born again of man (through the virgin womb of Mary) so that He could partake of our life; and we, who were born of man, are to be born again of God so that we might partake of His life and live by His Spirit.