1 Samuel 21:12

“And David laid up these words in his heart, etc.] Pondered upon them, and thought them over in his mind, finding that he was known, and his character also, and considered with himself what might be the consequence of this: and was sore afraid of Achish the king of Gath; lest he should be set against him, and be prevailed upon by his servants to take away his life, or deliver him up into the hands of Saul.”

“Was 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. He now learned by experience what he afterward taught us, Psa 118:9. It is better to trust in the Lord, than to put any confidence in princes. 1 Kings (1 Samuel) 21:15”

“21:12-13 The lengthy title of Ps 34 refers to this incident but names the Philistine king Abimelech rather than Achish. “Abimelech” might have been the common title for Philistine kings (in Hebrew it means “my father the king”). The name Abimelech also appears in Gen 20:2; 26:1.”

“laid up: Psa 119:11; Luk 2:19, Luk 2:51 sore: Sa1 21:10; Gen 12:11-13, Gen 26:7; Psa 34:4, Psa 56:3 1 Kings (1 Samuel) 21:13”

“But David took these words to heart, and was in great fear of Achish, lest he should treat him as an enemy, and kill him. In order to escape this danger, "he disguised his understanding (i.e., pretended to be out of his mind) in their eyes (i.e., before the courtiers of Achish), behaved insanely under their hands (when they tried to hold him as a madman), scribbled upon the door-wings, and let his spittle run down into his beard." The suffix to וישׁנּו is apparently superfluous, as the object, את־טעמו, follows immediately afterwards. But it may be accounted for from the circumstantiality of the conversation of every-day life, as in Sa2 14:6, and (though these cases are not perfectly…”