1 Samuel 17:48-51

48Then when the Philistine rose and began to advance, drawing near to meet David, David ran quickly toward the battle line to meet the Philistine.

49David put his hand in his bag, took from it a stone and slung it, striking the Philistine on his forehead. The stone sank into his forehead, so that he fell on his face to the ground.

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

51David ran, stood over the Philistine, picked up his sword, drew it from its sheath, slew him and cut off his head with it. When the Philistines saw that their champion was dead, they fled.