From the Word
41 Now while the Pharisees were gathered together, Jesus asked them a question, 42 saying, “What do you think of the Christ? Whose son is he?” They said to him, “The son of David.” 43 He said to them, “How is it then that David, inspired by the Spirit, calls him Lord, saying, 44 ‘The Lord said to my Lord, Sit at my right hand, till I put thy enemies under thy feet’? 45 If David thus calls him Lord, how is he his son?” 46 And no one was able to answer him a word, nor from that day did any one dare to ask him any more questions.
Matthew 22:41–46, RSV
Here Christ does not explain, but only says that David in his Psalm called Christ his Lord. “How then doth David in the Spirit call him Lord?” It does not sound right and it is contrary to nature for a father to call his son lord, be subject to him and serve him. Now David calls Christ his Lord, and to whom the Lord himself says: “Sit thou on my right hand until I make thine enemies thy footstool,” that is, be like me, acknowledged and worshiped as the right and true God; for it becometh none other to sit at his right hand; he is indeed so jealous that he allows no one to sit equal to him, as he says: “My glory will I not give to another.”
Since the Lord now makes Christ equal to himself, he must be above all creatures. Therefore he proposes to the Jews a great question, without solving it; for they did not understand it and the time had not yet come to make this publicly known. But the meaning is as our articles of faith teach us to believe, that Christ was both David’s true natural son, of his blood and flesh, and also David’s Lord, whom David himself must worship and hold as God. However, it was impossible to make these statements harmonize, as it is still impossible for human reason, where the Holy Spirit does not reveal it, to comprehend how the two should be at the same time in the one Christ, that he was truly David’s seed and God’s Son by nature.
Now Christ propounded this question to teach that it is not enough to have the law, which only shows from what state we have fallen; but that Christ must be born, not in sin as David and all men are born, but had to be born without man of the virgin, sanctified by the Holy Spirit, born a real, true man, yet without sin. He is the only man that has been able to keep and fulfil the law. This one must intercede in our behalf before God and be our right hand and protection, in whom we have forgiveness of sins and deliverance from God’s anger and hell. He also gives us the Holy Spirit to follow him until we come to him and be like him without any sin and in perfect righteousness.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 380–81.