I Samuel 17:37-40

Moreover David said, “The LORD, who delivered me from the paw of the lion and from the paw of the bear, He will deliver me from the hand of this Philistine.” And Saul said to David, “Go, and the LORD be with you!” So Saul clothed David with his armor, and he put a bronze helmet on his head; he also clothed him with a coat of mail. David fastened his sword to his armor and tried to walk, for he had not tested them. And David said to Saul, “I cannot walk with these, for I have not tested them.” So David took them off. Then he took his staff in his hand; and he chose for himself five smooth stones from the brook, and put them in a shepherd’s bag, in a pouch which he had, and his sling was in his hand. And he drew near to the Philistine.