1 Samuel 17:32-33, 37, 40-51
32And David said to Saul, "Let no man's heart fail because of him; your servant will go and fight with this Philistine."
33And Saul said to David, "You are not able to go against this Philistine to fight with him; for you are but a youth, and he has been a man of war from his youth."
37And David said, "The LORD who delivered me from the paw of the lion and from the paw of the bear, will deliver me from the hand of this Philistine." And Saul said to David, "Go, and the LORD be with you!"
40Then he took his staff in his hand, and chose five smooth stones from the brook, and put them in his shepherd's bag or wallet; his sling was in his hand, and he drew near to the Philistine.
41And the Philistine came on and drew near to David, with his shield-bearer in front of him.
42And when the Philistine looked, and saw David, he disdained him; for he was but a youth, ruddy and comely in appearance.
43And the Philistine said to David, "Am I a dog, that you come to me with sticks?" And the Philistine cursed David by his gods.
44The Philistine said to David, "Come to me, and I will give your flesh to the birds of the air and to the beasts of the field."
45Then David said to the Philistine, "You come to me with a sword and with a spear and with a javelin; but I come to you in the name of the LORD of hosts, the God of the armies of Israel, whom you have defied.
46This day the LORD will deliver you into my hand, and I will strike you down, and cut off your head; and I will give the dead bodies of the host of the Philistines this day to the birds of the air and to the wild beasts of the earth; that all the earth may know that there is a God in Israel,
47and that all this assembly may know that the LORD saves not with sword and spear; for the battle is the LORD'S and he will give you into our hand."
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.