1 Samuel 17:50-51

50So David triumphed over the Philistine with a sling and a stone; without a sword in his hand he struck down the Philistine and killed him.

51David ran and stood over him. He took hold of the Philistine’s sword and drew it from the sheath. After he killed him, he cut off his head with the sword. When the Philistines saw that their hero was dead, they turned and ran.