David’s lord is the Messiah.
David’s God is Yahweh.
David’s lord is presently sitting at the right hand of his and David’s God.
Yahweh said to David's Lord.....
-according to your theological premise, this is the Father talking to David's Lord (as King he has no earthly Lord)-- so this is the Father telling Jesus (whom you say is David's Lord) ---- Jesus? ---- You sit down at my right hand until I make your enemies beneath your feet.
How then (as asked by Jesus himself) can David's son be his Lord?