1 Samuel 17:48-51

48Then it happened, when the Philistine 1came closer to meet David, that 2David ran quickly toward the battle line to meet the Philistine. 49And David put his hand into his bag and took from it a stone and slung it, and struck the Philistine on his forehead. And the stone penetrated his forehead, and he fell on his face to the ground.

50So David prevailed over the Philistine with the sling and the stone: he struck the Philistine and killed him, and there was no sword in David’s hand. 51Then David ran and stood over the Philistine, and 3took his sword and drew it out of its sheath and finished him, and cut off his head with it. 4When the Philistines saw that their champion was dead, they fled.