ANSWER: The story of David and Goliath is found in the 17th chapter of 1st Samuel.
Then 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. This 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." (1Sa 17:45-46)