David himself calls him 'lord

As Jesus was teaching in the temple area he said,
"How do the scribes claim that the Christ is the son of David?
David himself, inspired by the Holy Spirit, said:
The Lord said to my lord,
'Sit at my right hand
until I place your enemies under your feet.'
David himself calls him 'lord';
so how is he his son?"
The great crowd heard this with delight. Mk 12:35-37