John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God...14 And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth...18 No one has ever seen God; the only God, who is at the Father's side, he has made him known. ESV
The Man Who God Became: John 1;1, 14, 18
Here John takes us back to before the creation of all things (Genesis 1:1). And there the Word was with God and was God. Meaning, Whom the Word was with the Word was. The Word, Who is God, became flesh and tabernacled among us. He pitched His tent. Similarly, in the days of Moses, God dwelt in the Tabernacle in the wilderness (Exodus 25:8-9, 33:7). An agent, a plan, another person or representative did not tabernacle therein, but God Himself.
Became flesh does not mean God ceased being God or that He even had divine flesh. It means He added to Himself humanity. God took on human nature to live among humanity, the One who is fully God and fully man. Glory refers back to the Old Testament where the presence of God was manifested in a variety of ways. This glory represented the very presence of God, and not an agent or representative of God.
The only Son from the Father: Jesus is also the Son of God, not in the sense of being a created being or merely a human body. But in the sense that a Son is exactly like His Father in all attributes. The term “only” here means unique or one of a kind, as in the case of Isaac, who is called Abraham's only son, but was not actually the only son of Abraham. Therefore, it implies the Son is unique or one of a kind.
No one has ever seen God, but the only God, who comes from the bosom of the Father declares Him. Meaning no one has ever seen God in a full or complete way. This is not two gods nor two separate persons but the Christ who reveals God is God Himself. I can say that no one can see the back of their head. That would be a true statement. Yet, with a mirror I can see the back of my head. Jesus reveals and explains God in a way that can be visible to the mortal eye. No mere man, angel or representative can do this. Jesus is the Almighty God in flesh.