1 Samuel 17:51 - Ellicott's Commentary On The Whole Bible

And when the Philistines saw their champion was dead, they fled. — The Philistines had agreed to consider this single combat as decisive. They had no fears as to its result, and when they saw their boasted champion fall they were seized with a sudden panic. Their adversaries, the children of Israel, on the other hand, seeing the unarmed shepherd boy with the head of the great warrior who had so long defied them in his hand, felt that the old power had come back to them, and that once more their Invisible King was with them, so they at once, with an irresistible shout, charged their dismayed foes, and the battle, as far as the Philistines were concerned, became a total rout.