The keynote in the mouth of every prophet-preacher, whether in Isaiah’s day or Jesus’ day or our day, is, “Your God reigns!” God is the king of the universe. God is the king of the universe. He has absolute Creator rights over this world and everyone in it. But there is rebellion and mutiny on all sides, and his authority is scorned by millions. So the Lord sends preachers into the world to cry out that God reigns, that he will not suffer his glory to be scorned indefinitely, that he will vindicate his name in great and terrible wrath, but that for now a full and free amnesty is offered to all the rebel subjects who will turn from their rebellion, call on him for mercy, bow before his throne, and swear allegiance and fealty to him forever. The amnesty is signed in the blood of his Son.
John Piper. The Supremacy of God in Preaching. Revised Edition. Baker Books, 2004.26-27.