Ladies: How many Philistine foreskins are you worth?
Jonathan, Saul's son, really loves David. So much so that they make secret pacts with each other, and Jonathan gives him all his clothes at one point. Hello? Leviticus? Anyone?
But David is still Saul's emissary, and gets sent out a lot on military forays. One day, the two of them come back from slaughtering the Philistines and the women come out, singing and dancing, encouraging them to kill even more. We get this lovely little quote: Saul hath slain his thousands, and David his ten thousands (v. 7). Yay?
Saul is pissed off, and from that moment, he hates David. He gets even crazier: he makes random prophecies then he throws a javelin across the room and says he's going to pin David to the wall with it. David understandably starts avoiding him. Saul is also afraid of David, because the people love him, so he also starts avoiding him.
Saul eventually offers his daughter Merab to David as a wife. David refuses, thinking he's unworthy as a son-in-law to the king, and she's given to someone else. Another of his daughters also has a thing for David, so Saul sets a trap: he tells his servants to tell David how much he favours him. David is skeptical, because he's so poor. The servants report this to Saul, who tells them to say he doesn't want any dowry but a hundred Philistine foreskins. Now, I have to say that if I found out my father had traded me for a hundred bits of severed penis-skin, I'd disown him, get divorced and start up a pottery shop, but I'm not a biblical character.
Saul of course thinks the Philistines will kill David, but he underestimates the boy. And David, ever the overachiever, brings back 200 foreskins, so he gives him his daughter. Saul becomes even more paranoid and afraid of David.
Frustrated by his previous effort, Saul tells Jonathan and all his servants to kill David. Jonathan warns him to hide. He'll go out to the fields in the morning and talk to his father about David. He pleads with him not to sin against his loyal servant. Saul actually listens and promises not to kill him. Jonathan calls David out from hiding and things go back to normal.
For awhile. But then there's another war with the Philistines, in which David is again triumphant. This causes the evil spirit to come back to Saul, and he picks up his javelin again. Jerry blames Saul for his mental illness, just in case you were, you know, planning to join his church or something. He throws it at David, who manages to escape. He sends messengers to his house, so his wife, Michal, advises him to hide some more.
Michal puts an 'image' on David's pillow, violating several commandments, and some goat hair in the bed. Ah, the old 'pillow body in the bed' trick. Works on me every time. Saul rebukes his daughter, and David escapes with Samuel.
Saul finds him, but this time when his messengers arrive, everybody's 'prophesying.' His messengers are taken by the spirit of the lord and join in. Likewise the next batch. Finally Saul himself comes down, but that pesky spirit won't leave him alone. He strips off his clothes and joins in the fun.