What does Luke 20:43 mean?

Jesus continues to quote Psalm 110:1. That Old Testament segment is difficult to untangle. The speaker is David, but he refers to someone in authority between himself and God. The word translated "LORD," in small-caps, of Psalm 110:1 is YHWH—the personal name of God. The word translated "Lord" is adōni and means "sir" or "master." Whom would David call "master"? But the "Lord" of Psalm 110:5 is a different word: Adōnai.

Many consider Psalm 110 to be a coronation hymn David wrote as he declared Solomon king. God certainly made Solomon's enemies his footstool. He had the most peaceful reign of any king of Israel. As Psalm 110:2 says, Solomon ruled in the midst of his enemies.

By using one verse of the psalm to reference the Messiah, Jesus infers the other verses apply, as well. It won't be until the writing of Hebrews, however, that the idea of the Messiah as "a priest forever after the order of Melchizedek" is fleshed out (Psalm 110:4; Hebrews 7). Psalm 110 describes David's descendant as an idealized king and a priest. Solomon doesn't fulfill that description, as no Jewish king was also a priest. A priest-king would certainly outrank David, even if the priest-king descended from David.

The Pharisees (Matthew 22:41) have no answer (Matthew 22:46). The people are delighted (Mark 12:37). Jesus isn't finished, though. He immediately follows with a warning about the religious leaders. Luke's version is short (Luke 20:45–47). Matthew's goes on for an entire chapter (Matthew 23). The scribes' attempts to discredit Jesus and their ungodly, prideful lifestyles reveal the fact that their ways lead to the death and utter destruction of their followers (Matthew 23:15). Their "righteousness" is shamed by the faith of a poor widow (Luke 21:1–4).