Jesus: How Can David Call His Descendant Lord?

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 footstool’ ”?    

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.
Matthew 22:41-46
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