"While the Pharisees were gathered together, Jesus asked them, saying, 'What do you think about the Christ? Whose Son is He?' They said to Him, 'The Son of David.' He said to them, 'How then does David in the Spirit call Him "Lord," saying: "The LORD said to my Lord, 'Sit at My right hand, till I make Your enemies Your footsool'"? If David then calls Him "Lord," how is He his Son?' And no one was able to answer Him a word, nor from that day on did anyone dare question Him anymore" (Matt. 22:41-46).
Jesus had been repeatedly questioned by the religious leaders. He now takes this opportunity to question them. However, His motive is not retaliation; He is seeking to teach them an important truth they need to learn; namely, that the Messiah would have a twofold nature--fleshly and divine.
"What do you think about the Christ? Whose Son is He?" - Notice that He doesn't ask them if they think He is the Messiah. He just asks them a general question about the Christ. They give the correct answer, but there is another aspect that they have not considered on this subject.
"How then does David in the Spirit call Him 'Lord'?" - That is, how could David call one of his descendants "Lord"? Jesus asks this question to focus their thoughts before He quotes the passage where David, while writing under inspiration of the Holy Spirit, does this very thing.
"The LORD said to my Lord" (cf. Psa. 110:1). Based on the lack of response by the Pharisees (cf. Matt. 22:46), it is safe to assume they believed that: (1) David was the author of Psalm 110 and (2) the meaning of Psalm 110 was Messianic. Thus, David had three individuals in mind: Jehovah, David himself, and David's Lord (i.e., the Messiah). The Pharisees would not deny this.
"Sit at My right hand till I make Your enemies Your footstool" - To sit at one's right hand indicates power and authority. God would exalt the Messiah to His right hand even though man rejected Him (cf. Acts 5:30,31). The Messiah (i.e., Jesus) will reign in heaven until all is surrendered to Him (cf. Heb. 10:12,13; I Cor. 15:25ff). To make one's enemies a "footstool" implies utter defeat and absolute subjection (e.g., Josh. 10:24,25).
"If David then calls Him 'Lord,' how is He his Son?" - Here Jesus asks them the converse of His previous question. The only way that either of these questions could be answered is by acknowledging both the divinity and humanity of the Messiah (cf. Rom. 1:3,4). This is something that the Jews in general seemed to be unable to do. They were so consumed with their worldly ideas of the Messiah as a royal descendant of David that they had lost sight of the prophesied fact that He would also be divine. If they had understood the true nature of the Messiah, they could have easily answered Jesus' question by saying: "As man, He is David's son (being physically born into this world after David); but as God, He is David's Lord (having always existed as deity)."
"And no one was able to answer Him a word, nor from that day on did anyone dare question Him anymore" - They wouldn't ask any more questions because it wasn't helpful to their cause. Now, instead of making an effort to defeat Jesus verbally, they would simply focus their energies on how they could kill Him!
"And the common people heard Him gladly" (Mark 12:37). Even today, it is generally the "common people" who are most receptive to God's truths (cf. I Cor. 1:26).