And he put all things under his feet and gave him as head over all things to the church, which is his body, the fullness of him who fills all in all. (Ephesians 1:22-23)
Adam was created to be the head of all things. In Genesis 1, God gave Adam dominion over the sea, the heavens, and the earth, and over every living thing. He was the covenental head, the federal head of all things, and when he grasped for glory, taking the fruit that would make him like God, he cast all creation into futility. Where the head is, the body follows. He took the responsibility of knowing good and evil without the maturity of being able to judge between them rightly.
Isaiah 49 reads as if it were written by the Son, telling Israel about a conversation he has had with the Father. “And he said to me, ‘You are my servant, Israel, in whom I will be glorified.’” It talks about the restoration of the kingdom, but not just of national Israel. It is expanded to again fill the world as it was under Adam. The people are given a new covenant head who rises up and draws all nations to himself. The land of promise is no longer sufficient to hold all the sons of the kingdom. He sets the captives free and overthrows his enemies.
In Colossians 1, Paul picks up these themes again. Christ is preeminent in all things, reconciling everything to himself as the new Adam, head of the new creation and of a restored humanity, which is his body, the church, as Paul points out twice in this chapter and also in the passage from Ephesians. Just as God was not satisfied to restore only the nation of Israel but extended his salvation to the world, so he is not satisfied with a people who are merely justified. Again, as the head is, so will the body be. He is the firstborn from the dead and we will be raised in him. He is the head of all things and all things will be put under our feet. In him the fullness of God was pleased to dwell. We have Christ in us, the hope of glory, of the fullness and maturity of the revealing of the sons of God.