David acts insane, letting drool dribble over his beard and onto the ground, and begins pounding his fists into the floor.
This image is from the Brick Testament, which is a hilarious source for Biblical material.
Over the time I've been reading the Bible again, I've learned that approaching the Bible strictly as a "moral code" is ridiculous, and that's just the wrong way to look at it. It's also wrong to take it seriously or literally. I suspect that's why so many Christians don't want to read the Bible from cover to cover; because shortly after the first two verses of Genesis, it loses credibility as a tale about reality and so we'd rather just hear the preacher's explanation instead.
However, if we look at it as a source of entertainment, where we can read about some really interesting behavior, the Bible is great. Sure, it's badly written, but once we stop taking it seriously, ironically it becomes easy to read. The cognitive dissonance goes away.
In this chapter of 1 Samuel, David is afraid of King Saul's wrath. If we remember, David is seen as something of a war hero because he killed Goliath on the battlefield. Now, he is seen as being chosen by God Himself. King Saul recognizes this and basically wants to kill David before he becomes a threat to his power.
David runs away, and in this chapter he even approaches the enemies of Israel (the kingdom of Gath) to escape from Saul. But some people in Gath recognized David since he was famous by that time, and called him out on it. He then acted like a madman, scribbling on some gates, drooling, and hitting the ground with his fists, just so they'd think he WASN'T David!
For some reason, he thought that if he acted like a mad man, they'd change their mind and protect him from Saul.
The chapter closes with Achish, who is the king of Gath, asking, "Have I need of madmen, that you brought this guy to me?"
Perhaps madmen were treated as entertainment back then? Or was he just being sarcastic? I guess we'll find out next time.