C. F. Keil and Franz Delitzsch on 1 Samuel 22:19

1Sa 22:19

But not content with even this revenge, Saul had the whole city of Nob destroyed, like a city that was laid under the ban (vid., Deu 13:13.). So completely did Saul identify his private revenge with the cause of Jehovah, that he avenged a supposed conspiracy against his own person as treason against Jehovah the God-king.