The understanding of this matter lies in recognizing and truly distinguishing the Law and the Gospel, that you may know that the teaching of the Law commands only what is to be done by the ungodly and lost, as 1 Tim. 1:9 says: “The Law is not laid down for the just but for the lawless.” But where the godly are, there the Law, which is intended only for the humiliation of the ungodly through the recognition of their sin and weakness, is already abolished. The Gospel teaches from what source you receive the power to fulfill the Law. In this respect it commands nothing; nor does it force the spirit, which hastens of its own accord by faith. It adds some commands, but it does so to kill the remnants of the old man in the flesh, which is not yet justified. From these commands, however, the spirit is free, being satisfied with faith alone. Of this matter we have spoken amply elsewhere.7
Now let us look at the words: “The Lord your God will raise up for you a Prophet like me from among you, from your brethren—Him you shall heed.” Here he prophesies that Christ will be true man and will come from the blood of the Jews, because salvation is from the Jews (John 4:22). No one has ever arisen from this people who taught a different word from the word of Moses and set up a new ministry except this one Christ of ours. However many prophets there were before Him, they all preserved and taught Moses. This Prophet freed not only the Jews from Moses but all nations throughout the world and gave them the new Word of the Gospel. That He was from the Jews, both the Gentiles and the Jews being witnesses, proves that it is He of whom Moses speaks here, and that this prophecy is fulfilled in Him.
Luther’s works, vol. 9: Lectures on Deuteronomy 1525