The Lord is asked an apparently honest question about which Bible verse carries the most weight. The answer He gives challenges all of us to love the God Who loves us and died for us, with all our might.
David was nowhere near the battlefield where King Saul and his sons died in battle. News reached David days later by an Amalekite who admitted to striking a deathblow on Saul, for which David executed him.
Again the religious leaders came in attempt to discredit and trap Jesus in His words. Again He silences them with reason from the Scripture so that the coalition against Him and the questions they hurled backfired.
King Saul was so distracted by his hatred for David that he neglected his duties as King, leaving Israel ill prepared to face the Philistine invasion. Saul and his sons perished in battle, finally ending the era of Saul.
After the Lord silenced challengers to His authority and put them on defense in the exchange, He intensified His attack and used the vineyard metaphor from Isa 5 to point out the criminal behavior of Israel’s leaders.