“The Word became flesh and dwelt among us. We observed his glory, the glory as the one and only Son from the Father, full of grace and truth.” - John 1:14 CSB
Right here, John lays it out so plainly for us to see that beyond a shadow of a doubt, Jesus is the Word of God. John testifies to his own observance of the glory of God through the person of Jesus as the one and only Son of God. The very voice of the Father in Heaven became flesh and is walking the earth, living right alongside John and he himself is so overjoyed by it that he has to write it down to share with the entire world.
Let me quickly try to explain why this would have been so earth shattering for John and his peers: the God they had been raised to believe in and follow, was only accessible through their rituals, through the high priests, through sacrifices. Many would have spent their lifetimes studying the scrolls of the prophets and other historical writings that had been carried through their lineage to help them see and understand who God is. Many of these rituals and traditions that they would have known would have been developed because of a long period of silence for the people of Israel when they did not have any prophets bringing the word of God to them. For that Word that they so longed for and sought after through their traditions and rituals to become flesh as they are flesh and walk with them would have been absolutely astonishing and mind blowing for any who could see it and accept it.
