What does Luke 20:18 mean?

Jesus finishes His warning to the Jewish leaders, as well as to the Jewish people who are listening. In the parable of the tenants, Jesus gives an allegory. Throughout history, the people of Israel had rejected God's prophets and would soon kill His very Son. The leaders will do so to maintain their authority and to keep gathering money and honor from the people. But if they reject God's Son, God will reject them, removing their authority and destroying them. He will replace them with better tenants (Luke 20:9–16; Matthew 21:41).

When the crowd reacts, Jesus responds by quoting Psalm 118:22: "The stone that the builders rejected has become the cornerstone." Jesus was always the cornerstone. His death and resurrection make it possible for people to be God's people. The builders—the Jewish leaders—don't have to reject Him. Some won't (Mark 15:43; John 3:1–3; Acts 6:7).

Everyone who rejects Christ, however, will be destroyed (John 3:36). Jesus' death and resurrection will prove to be an obstacle to the Jewish people. It's a concept they cannot get past to continue in their journey with God (1 Corinthians 1:23).

The chief priests and the scribes understand what Jesus is saying. They know He is telling them God is going to destroy and replace them. Instead of taking the warning to heart, they continue their mission to destroy Jesus (Luke 20:19–20). But they're afraid of the people. So, they try to turn the people against Him by challenging His authority, first in His legal interpretations (Luke 20:21–26) and then in His doctrinal teachings (Luke 20:27–40). Jesus counters by proving the authority of the Christ—Himself—is greater than even King David (Luke 20:41–44).