According to the Hebrew idiom, this “staff” means a royal scepter, as in Gen. 47:31 and Heb. 11:21: “He bowed in worship over the head of his staff,” which Jerome has translated with “he turned toward the head of his bed.” In Greek it is called a scepter; in Latin it is called a staff. Thus in Esther 5:2: “He held out the golden staff which he held in his hand, and Esther approached and kissed the top of the staff.” This is the “rod of iron” with which Christ rules us and “dashes in pieces like a potter’s vessel” the carnal and old man (Ps. 2:9). Concerning this staff Ps. 110:2 also states: “The Lord will send forth from Zion Thy mighty staff. Rule in the midst, etc.” Is. 2:3 and Micah 4:2 interpret this in the following way: “Out of Zion shall go forth the Law, and the Word of the Lord from Jerusalem.” And in Rom. 1:16 the apostle says: “For I am not ashamed of the Gospel, for it is the power of God for salvation to everyone who has faith.” Therefore although others interpret this staff to mean inflexible power, as it seems to be, actually, however, it is nothing else than the same Gospel, namely, the Gospel itself or the Word of God. For Christ rules the church with no other power than the Word, as it is written (Ps. 33:6): “By the Word of the Lord the heavens were made.” But it is called “a staff of justice,” that is, of rectitude, or, what is the same thing according to the Hebrew idiom, “of just guidance,” which in Latin would be called virga equa, recta, directa, etc., as when Ps. 21:3 says, “with blessings of goodness.” In Latin we would say in benedicionibus dulcibus. Therefore it is called “the staff of Thy kingdom” to distinguish it from all other kingdoms, even from the kingdom of the synagog, though this kingdom had the Law of God. Their staffs are crooked and unjust. But only Thy staff is “a staff of rectitude.” For absolutely no doctrine, be it civil, ecclesiastical, or philosophical and in any way human, can direct man and make him upright, since it leads only so far that it establishes good behavior, while man remains as he has been of old. And so of necessity it makes nothing but pretenders and hypocrites; for those dregs of the heart and that bilge water of the old man, namely, love of himself, remain. Therefore it deserves to be called an evil doctrine, since it is not able to offer rectitude. But the Gospel says: “Unless one is born again of water and the Spirit, he cannot enter the kingdom of heaven” (John 3:5). And thus the Gospel preserves nothing of the old man but destroys him completely and makes him new, until hatred of himself utterly roots out love of himself through faith in Christ. Therefore all boasting of erudition, wisdom, and knowledge is useless; for no one is made better by these, no matter what good and laudable gifts of God they are. Indeed, besides the fact that they do not make a man good, they become a covering for wickedness and a veil over the disease of nature, so that those who are pleased with themselves because of them and seem to themselves to be good and sound are incurable.
Luther, M. (1999, c1968). Vol. 29: Luther’s works, vol. 29 : Lectures on Titus, Philemon, and Hebrews (J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed.). Luther’s Works (29:118). Saint Louis: Concordia Publishing House.