and David arose and went, he and his men, and killed of the Philistines two hundred men; and David brought their foreskins, and they gave them in full number to the king, that he might be the king's son-in-law. Saul gave him Michal his daughter as wife.
Though he was just a very young fellow, he was set over a part of the army and these guys respected him so much, of course God's deliverance of the Philistine in his hand, that they just accepted him, but then trouble began to arise.