1 Samuel 17:48-51

48When the Philistine arose and came and drew near to meet David, David ran quickly toward the battle line to meet the Philistine.

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

50So David prevailed over the Philistine with a sling and with a stone, and struck the Philistine and killed him. 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 its sheath and killed him and cut off his head with it. When the Philistines saw that their champion was dead, they fled.