1 Samuel 17:47

43 “Am I a dog,” he said to David, “that you come at me with sticks?” And the Philistine cursed David by his gods.

44 “Come here,” he called to David, “and I will give your flesh to the birds of the air and the beasts of the field!”

45 But David said to the Philistine, “You come against me with sword and spear and javelin, but I come against you in the name of the LORD of Hosts, the God of the armies of Israel, whom you have defied.

46 This day the LORD will deliver you into my hand. This day I will strike you down, cut off your head, and give the carcasses of the Philistines to the birds of the air and the creatures of the earth. Then the whole world will know that there is a God in Israel.

47 And all those assembled here will know that it is not by sword or spear that the LORD saves; for the battle is the LORD’s, and He will give all of you into our hands.”

48 As the Philistine started forward to attack him, David ran quickly toward the battle line to meet him.

49 Then David reached into his bag, took out a stone, and slung it, striking the Philistine on the forehead. The stone sank into his forehead, and he fell facedown on the ground.

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

51 David ran and stood over him. He grabbed the Philistine’s sword and pulled it from its sheath and killed him; and he cut off his head with the sword. When the Philistines saw that their hero was dead, they turned and ran.

Read all of 1 Samuel 17