I Samuel 17:49-51

Then David put his hand in his bag and took out a stone; and he slung it and struck the Philistine in his forehead, so that the stone sank into his forehead, and he fell on his face to the earth. So David prevailed over the Philistine with a sling and a stone, and struck the Philistine and killed him. But there was no sword in the hand of David. Therefore David ran and stood over the Philistine, took his sword and drew it out of its sheath and killed him, and cut off his head with it. And when the Philistines saw that their champion was dead, they fled.