In his flight from the murderous rage of Saul, David found himself in Gath. And in 1 Samuel 21:10-15, we see the brief account of his stay there. This account begins with the explanation of David’s arrival in the land, but then notes that the servants of the king recognized him and noted the songs sung about David and how he had slain his “tens of thousands.” The Bible tells us that David took their words to heart and became very afraid of the king. Why is this? If the king’s servants had recognized him as a hero, why would David be afraid?
The answer is simply a matter of perspective. David was a hero to Israel. The songs sung were about him slaying tens of thousands of Philistines, but now David finds himself in Gath, a major Philistine city. He’s recognized as a famous slayer of their people, and he also happened to be carrying the trophy of Goliath’s sword with him at the time. If ever someone’s presence would be offending to the local population, it was at that very moment. David was right to be concerned about his situation.
In David’s case, the insanity defense worked. We have to remember, King Achish was not Jewish. He was a Philistine, and his perspective on things would have been different than from that of the Israelites. In the ancient pagan world, it was believed that, if someone was mentally ill, their malady must have come from some type of evil force. The insane then were generally given a wide berth because it was believed that, if you did harm to the person under control of an evil power, that evil power would likely turn its attention on you. David’s performance must have been convincing enough to keep him safe. Seeing his behavior, Achish became greatly distressed and likely had David removed from his house.