Mat 22:42 What do you think of the Christ? whose son is he?
Mat 22:43 How then did David in spirit call him Lord, saying,
Mat 22:44 The LORD said unto my Lord, Sit you on my right hand, until I make your enemies your footstool?
Mat 22:45 If David then call him Lord, how is he his son?

This chapter began with a king giving a wedding feast for his son. It then discusses the nature of earthly authority and the afterlife. It ends with a discussion of another king's son: the Messiah, who was expected to be the son of David. These final verses bring together this seeming range of topics together an important conclusion.

The Jews of Jesus's era thought they understood who the Messiah was and the source of his authority. He was a decendant of David, and his authority came from David as "the annointed" king of the Jews.

Here, Christ demonstrates that, according to Jewish tradition itself, David recognized the Messiah's authority as superior to his own. By Jewish law and custom, a son cannot be master to his own father. The term used here for "lord" is kurios, which means "master" (see below). The general assumption here, and in the tradition of the times, was that authority passed from father to son. Thus, the original question about the Messiah's father was a question about the source of Christ's authority.

Note that Christ doesn't answer his own question nor does anyone ask him to. Instead, Christ simply makes it clear that on this central question of authority, the traditional Jewish viewpoints were insufficient.

In the end, this chapter comes to one conclusion: that all authority comes from God. Intermediary authorities, such as earthly kings, must be respected, but only within their own realms. There is a strong hint here that the realm of the Messiah reaches beyond this world to the next. The only other place in the Gospels that Christ mentions a "footstool" is when he referred to the earth as God's foodstool.

"Spirit" is pneuma, which means "blast," "wind," "breath," "the breath of life," and "divine inspiration." In this case, it means that David was speaking under divine inspiration.

The only word that we might expand on is kurios, which means "having power," "being in authority" and "being in posession of." It also means "lord," "master of the house," and "head of the family." In the original verse quoted, Psa 110:1, two different words were used in the Hebrew translated into Greek as kurios, Y-hova for the first LORD and 'adown for the second. Kurios and 'adown are very similar in meaning, referring to whoever is in authority in a given situation.

"Footstool" is from hupopodion, which means "footstool."