Say to the cities of Judah: Behold your God! He mentions the doctrine that should be preached. This is the gist of your preaching: Behold your God! “Promote God alone, His mercy and grace. Preach Me alone.” The rest, the ungodly, preach the doctrines and works of men, their own rules and righteousnesses. This herald must avoid that kind of teaching and speak of Christ alone. In Him alone rests all our salvation.
Luther’s Works Vol. 17: Lectures on Isaiah Chapters 40-66