I Samuel - Chapter 18
An Unusual Dowry
David became great friends with Shaul's son Jonathan (Yonason). After the victory over Goliath, David was drafted to Shaul's service full-time, so he no longer commuted between his family and the king. David became renowned as a great warrior and the people composed a song in his honor, the refrain of which went, "Shaul has slain thousands, but David has slain tens of thousands." This did not sit well with Shaul, who considered the possibility that David was his foretold successor.
The next day, Shaul was suffering from his depression and David was playing the harp to calm him. Shaul took the opportunity to throw his spear at David, figuring that his mental illness would be blamed. Even though he was a crack shot with a spear, G-d made him miss David at point-blank range. David continued to be successful and Shaul continued to grow jealous of David.
Shaul decided to offer David his daughter Merav as a wife. (David had not pursued the offer from killing Goliath because he did not consider himself worthy of such an honor.) It turned out that Merav was betrothed to someone else, but Shaul's daughter Michal wanted to marry David. When David replied that he could not offer an appropriate dowry for the king's daughter, Shaul said that all he wanted was 100 Philistine foreskins. Shaul fully expected David to be killed while trying to raise this unusual dowry.
G-d favored David, who killed 200 of the enemy and returned quickly with twice the dowry he had promised. Shaul understood that David had G-d on his side and that his daughter loved David. Of course, this only made him more paranoid.
It's interesting to note that when the Navi speaks of Jonathan in the context of his friendship with David, he is called "Yehonason" rather than "Yonason" - there is a letter Hey added to his name. The letter Hey represents G-d. (It's the letter that was added to Abram and Sarai's names when they became Abraham and Sarah.) The added Hey when speaking of the love between David and Jonathan is a symbol of how G-d rests upon such selfless relationships.