1 Samuel 17:37

He will deliver. Saul had once asked great things of God and had attempted great things for Him. However, pride and self-glory had filled his heart, and now every obstacle appeared insurmountable. In his effort to vindicate himself he had forgotten that with God all things are possible. How could God better impress upon him his lack than by letting David rehearse the providential protection that had been over him personally in the past. The Spirit of God once took possession of Saul. Now he would have the opportunity of seeing what he himself might have been had he not rebelled against that Spirit. Again he was in a dilemma. If he refused to let David fight, the army would expect him, as king, to champion their cause. If he let David fight, and Goliath killed him, the battle would be lost and Israel would again be in bondage to the Philistines. It was to save his own life and reputation that Saul sent David forth to combat. But the very means Saul used in an effort to save his reputation as king and leader resulted in its loss (ch. 18:6-9). It became apparent that without God, Saul was powerless before his enemies (ch. 14:24; cf. 15:23), and that past victories for which he had personally taken credit were from God.