David knows he can run from Saul only so long. Israel isn’t big enough to allow for the peaceful co-existence of two such adversaries, so David determines to leave. The Philistines have been a thorn in Saul’s side for the entirety of his reign. Where better to hide than among your enemies in plain sight?
Saul has been adding mighty and brave men to his army from wherever he can find them (1 Samuel 14:52). Why shouldn’t the Philistine king? And who better to add than this valiant and successful soldier David who is the sworn enemy of Israel’s king?
This puts, of course, David in an awkward position. As long as Achish and Saul don’t go to war, David is fine. If, however, war breaks out, David is doomed. He can’t fight against Saul without risking alienation from Israel. He can’t fight against Achish without risking his own security.
Fortunately, when the inevitable happens (chapter 29), Achish’s own generals object to David’s presence and David and his band are sent home, back to Ziklag (about 20 miles east of Gaza). There is a subtle twist in David’s feigned disappointment with Achish. He asks: “Why can’t I go and fight against the enemies of my lord the king?” Achish no doubt thinks David means Achish’s enemies. David, however, means Saul’s enemies.
How fortuitous that Achish’s generals objected to David’s presence! Or perhaps it was not fortuitous at all, but the working of God to accomplish what Saul has not: the destruction of the Amalakites (chapter 30).