1 Samuel 17

The Philistines and Israelites face off across a valley. The Philistine giant, Goliath of Gath, challenges Israel to send one man to fight him, determining the winner of the war. David, sent to the camp to bring food to his brothers, is outraged by Goliath's blasphemy against the living God. David, armed only with a sling and five stones, declares that God will deliver the giant into his hand. David strikes Goliath in the forehead with a stone, killing him instantly, and then uses Goliath's own sword to cut off his head, resulting in a rout of the Philistine army.