What does Matthew 22:43 mean?
Jesus has turned the tables on the Pharisees (Matthew 22:15, 34–35) and is asking them a question. It seems to be an easy one at first glance. He has asked whose son the Christ—or Messiah—is. They have immediately answered from the prophetic Scriptures that the Christ is the son of David. By this, they mean that the Messiah will be directly descended from King David (Isaiah 11:1, 10; Jeremiah 23:5; 33:15).Matthew demonstrated that Jesus was descended from David in the first chapter of this book (Matthew 1:1, 17). Jesus does not disagree with them, but He does ask them a follow-up question that complicates the answer. This point emphasizes the divinity of Christ, and strongly implies the concept we now refer to as the Trinity.
Jesus asks why David, under the inspiration of the Spirit of God, calls the Christ "Lord"? Jesus quotes from Psalm 110, written by King David, in the following verse. With the statement that David wrote these words "in the Spirit," Jesus affirms that Psalm 110 was truly written by King David and that it was written under the inspiration of the Holy Spirit as all Scripture is (2 Timothy 3:16–17).
In other words, Jesus' question is how the ancestor, David, would call his own descendant "Lord." That implies the Christ was more honored than David himself in some way. Jesus' question implies that perhaps it matters who else might call the Christ "Son."