This verse completes the question Jesus began in Matthew 22:43: "How then doth David in spirit call him Lord, saying..." He quotes David's own words so the Pharisees must deal with Scripture, not with Jesus' opinion. "In spirit" means, as Barnes says, "By the inspiration of the Holy Spirit." Gill explains the point: David calling the Messiah Lord "supposes him to be more than barely his son, and to be a greater person than himself." Jesus pressed them to explain why a king would call his own descendant "my Lord."

Jesus pressed the point with one more question: "If David then call him Lord, how is he his son?" (Matthew 22:45). Then the text says, "no man was able to answer him a word, neither durst any man from that day forth ask him any more questions" (Matthew 22:46). The psalm they knew well had become a question they could not answer.

In Psalm 110:1, the first "LORD" (in capitals) is the Hebrew Yahweh, God's own name. The second, "my Lord," is adon, a word for a lord or master. So David pictures God speaking to someone David himself calls his master.

To sit at a king's right hand was, in Barnes' words, "significant of favor, trust, and power." A footstool pictures enemies brought fully under the ruler. Keil & Delitzsch, commenting on Psalm 110:1, call this sitting "exaltation to a participation in God's reigning," and they read the psalm as "not a declaration of the people concerning David, but of David concerning Christ." The Greek text behind the KJV (the Textus Receptus) reads hupopodion, footstool, as in the psalm. Some other Greek editions read hupokato, under, which is why the ESV says "under your feet."

Jesus did not invent a new teaching here. He opened a door already in Scripture. David, speaking by the Spirit, heard God invite the Messiah to sit beside Him and share His rule. The Son of David is also the One David worships.

The psalm also looks ahead. The One invited to sit at God's right hand would see His enemies subdued. After the resurrection, Peter quoted this same verse and concluded that "God hath made that same Jesus, whom ye have crucified, both Lord and Christ" (Acts 2:34-36). The question Jesus left hanging in the temple is answered by His exaltation.