Bible Notes Online - 1-Samuel 27 - ESV
Commentary

v1: David clearly did not believe Saul. He doubted Saul's words, and feared that he would soon be pursuing him again. But David did not pray, he returned to his introspection, as in 21.10-15. David believed the safest place for him would be in Philistia; where he had previously feigned madness (21.10-15). In contrast, David was accepted this time.

v2-4: For 16 months, David sat in the seat of the scornful, but Saul stopped chasing him.

v5-7: David and his men lived in Ziklag, a town belonging to Simeon. Such are the kisses of the enemy (Prov 27.6), giving something that was stolen. Initially David enjoyed prosperity, but he soon lost it, see 30.1-5. The way of the world may appear attractive, but its end is disaster.

v8-12: David's deceit, to keep in with Achish. He became unusually ruthless to cover his deception. He declared that his attacks were within Israel. Achish was taken in, and invited David to join his army (see 28.1-2); beware of the approval of the world (Luke 6.26).