1 Samuel 18:17-30, 1 Samuel 19
..... But Saul thought to make David fall by the hands of the Philistines....
By this point, Saul wanted David killed. Saul recognized David's anointing. He recognized that, that was once his anointing and wanted to kill David because he now had it... Saul however, was a smart man. While he wanted to kill him, he knew he couldn't be the on to do it because David had God's anointing. Saul gets this idea to have the Philistines do it. This was supposed to be accomplished by David going out and actively seeking the Philistine's to attack and kill them as apart of the price for marrying his daughter.
What happens is, not only does David get the actual price, but he's able to go above and beyond what was asked. Because of this, Saul knew, and was beginning to learn exactly what and who David is and what he was destined to be.
Because Saul kept trying to kill David, David had to run. He had to flee, and in the process of his fleeing, he had to rely on God. This is when David writes a bunch of the Psalms that he has been credited with. During this process, David grows. David learns things about what he needs to do in order to have a successful kingdom. David had to go through this before he could become king. God had to remove him from all distractions, to get him to rely solely on him. David had to go through God's kindle. He had to be molded, and shaped and formed, but God couldn't do this while things were good. He had to go through the fire... and because of this, we know of him as a "Man after God's own heart..."
