Luke 20:44

David therefore calleth him Lord, how is he then his son?

David spoke by the Spirit of inspiration when he called the Messiah Lord. Prophecy had identified the coming Messiah as David's descendant and given him the position of David's son, with the title son of David. Yet he is both David's descendant and David's Lord, more than merely a human man descended from David, the divine Son of God. Jesus put the question to challenge and test the Pharisees over whether they recognized his divinity, that the Messiah was more than a man, and they were unable to answer it.

The question belongs to Jesus' illustrations and warnings about rejecting the Son of God. Its warning applies to people in every age who refuse to receive Christ as their Redeemer, that unless they repent the doom foreshadowed by those warnings will be theirs.