In the beginning was the Word, and the Word was with God, and the Word was God. He was with God in the beginning. Through him all things were made; without him nothing was made that has been made.This is one of those passages that shows the big picture of God's plan. The mystery of the Trinity is made known, in part, with the first verse of this Gospel account of Jesus. This passage connects everything together, both Testaments, from the creation of the world in the first chapter, the law and Moses, and right into the message of grace found in Christ.
... The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only [Son], who came from the Father, full of grace and truth.
... to all who did receive him, to those who believed in his name, he gave the right to become children of God— children born not of natural descent, nor of human decision or a husband's will, but born of God.
... For the law was given through Moses; grace and truth came through Jesus Christ.
The Law came to man through Moses and is recorded in the Old Testament. It established God's standard for all people. Israel failed to keep it and if we are honest we all fall short of God's standard. God sent his Son Jesus, as recorded in the New Testament, to pay the price for all of our failings so we can come near to God and enjoy his presence forever. Paul puts it this way in his letter to the Romans.