He wasn't "reborn", He didn't pre-exist as a man on the earth. He has always been with the Father in heaven. The Bible teaches this throughout the entire thing. I could post several pages of verses to show this. But I've already posted some of them, and you seem to ignore them.
He had to become flesh in order to be able to shed blood so that our souls could be redeemed. The blood is the atonement of the soul, as it says in the Old Testament.
Leviticus 17:11
For the life of the flesh
is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it
is the blood
that maketh an atonement for the soul.
If Jesus hadn't become flesh, He could not have shed His blood, which was necessary for the atonement of our souls. It had to be sinless blood, so no man but Christ could do this, because no man but Christ is sinless. So the word of God, who was with God, and who was God, became flesh, and is Jesus Christ.