If David then call him Lord, how is he his son?

People's New Testament

22:45 How is he his son? The answer is not given here, but plain. Christ, the Son of David, according to earthly descent, is the Son of God, God manifest in the flesh.

Matthew Henry's Concise Commentary

22:41-46 When Christ baffled his enemies, he asked what thoughts they had of the promised Messiah? How he could be the Son of David and yet his Lord? He quotes Ps 110:1. If the Christ was to be a mere man, who would not exist till many ages after David's death, how could his forefather call him Lord? The Pharisees could not answer it. Nor can any solve the difficulty except he allows the Messiah to be the Son of God, and David's Lord equally with the Father. He took upon him human nature, and so became God manifested in the flesh; in this sense he is the Son of man and the Son of David. It behoves us above all things seriously to inquire, What think we of Christ? Is he altogether glorious in our eyes, and precious to our hearts? May Christ be our joy, our confidence, our all. May we daily be made more like to him, and more devoted to his service.