The first verse of this chapter has been called “God’s favorite Bible verse,” for it is quoted more than any other Old Testament passage in the New Testament. The Psalm is quoted altogether 23 times, in 11 books, by 7 of the 9 authors. Perhaps the most clarifying moment was when Jesus himself quoted it in a dispute about his own nature (Matthew 22:41-45). Jesus understood the speaker of verse 1 to be King David observing (somehow) a conversation between “the LORD” - Yahweh, God - and someone else who is David’s “Lord.” A different English translation of verse 1 could be, “God said to my Master . . .”
Yet the Old Testament also says that the Messiah will be “David’s son” - his descendant. So Jesus asks, “If he is David’s son, how is it then that David calls him his ‘Lord’?” This question goes to the dual nature of Christ. Though he is the Christ, he is also descended from David. Though he is a king, he is also a priest, who descends from a priesthood that’s older anything Jewish.
For in Genesis 14, before there ever was an “Israel,” a priest named Melchizedek comes down from a city named “Salem” - perhaps a forerunner of Jerusalem? - and Abraham pays him a tithe. This priest then goes away and is never heard of again until Psalm 110:4. In a book where everyone else lives XX years and then dies, Melchizedek stands alone, with no mention of a birth or death - his priesthood has no beginning nor end. What does it all mean?
We can conclude - strictly from reading our Bibles to the point of Psalm 110 - that this “Lord” is both a Great High King and a Great High Priest. We keep reading and we realize that he is Jesus, who fulfilled verse 1 when he ascended to the Father’s right hand after his crucifixion and resurrection. He descended from David through his earthly mother and father, but through his ascension, he became David’s King. As a man, he was the perfect sacrifice. Now he reigns over the nations.
We now live in the age of Psalm 110:1, under the reign of King Jesus. One day he will fulfill verses 5-7. Until then we purify ourselves and offer the world the clean water, broken bread and rich wine of his sacrifice, that our King might rule in the midst of his enemies.