1 Samuel 17:48-51

48As the Philistine started forward to attack him, David ran quickly toward the battle line to meet him. 49Then David reached into his bag, took out a stone, and slung it, striking the Philistine on the forehead. The stone sank into his forehead, and he fell facedown on the ground.

50Thus David prevailed over the Philistine with a sling and a stone; without a sword in his hand he struck down the Philistine and killed him. 51David ran and stood over him. He grabbed the Philistine’s sword and pulled it from its sheath and killed him, and he cut off his head with the sword.

When the Philistines saw that their hero was dead, they turned and ran.