It happened on the next day, that an evil spirit from God came mightily on Saul, and he prophesied in the midst of the house: and David played with his hand, as he did day by day. Saul had his spear in his hand;
He set up a dowry regarding the Philistines. David went out and gave him double dowry. So Saul then of course was sort of shocked and surprised. He figured David would get wiped out in going out against the Philistines.