I Samuel - Chapter 21

Jonathan went home and David took his forces to Nov, a city of Kohanim (Jewish "priests" - descendants of Aaron). He told Achimelech that he was on a secret mission for Shaul and asked for food for his troops. Achimelech told David that all he had was "sacred bread" (probably the lechem hapanim - the "show bread" placed on the Table every week), but that David could have it if his men had not been with women.

Shaul had a faithful officer named Doeg, who happened to be worshipping in Nov and witnessed this transaction between David and Achimelech. File that piece of information away; it's going to be important later.

David also asked if there were any weapons in Nov they might take. All they had was Goliath's sword, which had been placed behind the ephod. They were reluctant to part with it, but who was more entitled to it than David? David took it and ran to Gath.

Seeking refuge in Gath was perhaps not David's smartest move, since Goliath (whom David killed) was from Gath. The people recognized him and reported to Achish, the king of Gath, that David was in town. They brought him to Achish, but David faked having a mental illness (which is definitely not cool by our standards but was a necessary ruse for David). Achish either refused to believe that this was David or he figured that punishing him was pointless; in either case, he sent David away. This incident is the basis of Psalm 34, "A Psalm of David when he feigned madness before Avimelech, who drove him away and he departed." ("Avimelech" in this case is a title, like all Egyptian kings were called Pharaoh.)

When David was brought before him, Achish said, "Do I have any shortage of people with mental illnesses in my house?" The Midrash tells us that this was more than a rhetorical question; Achish had a wife and a daughter who had mental illnesses. He decided that his hands were pretty full just taking care of his family members, so he sent David away.