1 Samuel 21:12 - Joseph Benson’s Commentary on the Old and New Testaments

David laid up these words in his heart It is probable he had been at first well received, but this discourse deeply affected him, and made him think himself not safe there. For, when he found that his fame was spread among them, as having slain such numbers of the Philistines, he concluded that they would be instigated to take revenge on him now they had him in their power. And was sore afraid Lest either their revenge or policy should prompt them to kill him. Perhaps he was the more apprehensive, because he wore Goliath's sword, which was, probably, well known at Gath.