1 Samuel 17:48-51

48When the Philistine rose and came forward to meet David, David ran quickly toward the battle line to meet the Philistine.

49David put his hand into his bag and took out a stone and slung it, and it struck the Philistine on his forehead. The stone penetrated his forehead, and he fell face down on the ground.

50So David triumphed over the Philistine with a sling and a stone, and he struck down the Philistine and killed him; but there was no sword in David’s hand.

51So he ran and stood over the Philistine, grasped his sword and drew it out of its sheath and killed him, and cut off his head with it. When the Philistines saw that their [mighty] champion was dead, they fled.