1 Samuel 17:48-51

48And it came to pass, when the Philistine arose, and came and drew nigh to meet David, that David hastened, and ran toward the army to meet the Philistine. 49And David put his hand in his bag, and took thence a stone, and slang it, and smote the Philistine in his forehead; and the stone sank into his forehead, and he fell upon his face to the earth.

50So David prevailed over the Philistine with a sling and with a stone, and smote the Philistine, and slew him; but there was no sword in the hand of David. 51Then David ran, and stood over the Philistine, and took his sword, and drew it out of the sheath thereof, and slew him, and cut off his head therewith. And when the Philistines saw that their champion was dead, they fled.