As the second member of the Trinity, Jesus is God. Being God, Jesus enjoys all of the amazing fullness of the Father and is one with the Father, and yet mysteriously is somehow separate from the Father in nature. The oneness and separateness of the Godhead is on display in Psalm 110 as it begins in a somewhat confusing way. “The Lord says to my Lord”. This is David, the king, writing, and who could be David’s Lord apart from God? So when David writes “the Lord says to my Lord”, one is tempted to think there are two lords. The mystery is solved when read in its original Hebrew. The phrase reads “Jehovah says to my Adonai sit at my feet until I make your enemies a footstool.” Jehovah of course is God the Father, the great I Am. Adonai translates as lord, master, sovereign, controller. In essence, David is saying “Jehovah says to my master”. But David had no earthly master, as king of Israel, he answered to no one but God. David’s master could only be the Messiah.
We have established that the one David referred to as his Adonai is the Messiah, yet how do we know David is referring specifically to Jesus? He didn’t use the name of Jesus, and of course he had never met Jesus. We could claim divine inspiration because, in fact, David would have to be divinely inspired to discern the two members of the Trinity spoken of in the psalm. Luckily this isn’t necessary as Jesus has answered the question for us. In Mark 12:35-37 Jesus said that David was indeed inspired when he spoke the words in Psalm 110. The scribes and Pharisees commonly taught that the Messiah would be the earthly son of David. But Jesus asks them all, if the Messiah is David’s son, then why does he call him Lord? Jesus’ question refers to the fact that, while He was a descendant of David through Mary, He was not David’s earthly son. He was the son of God and as such David’s Lord!
Later, in one of the first sermons ever taught, Peter quotes Psalm 1 and reminds the people that even though David never ascended to heaven he saw that Jesus was at the right hand of God and that He was indeed Messiah.