1 Samuel 17:32-40 New Revised Standard Version (NRSV)
32 David said to Saul, “Let no one’s heart fail because of him; your servant will go and fight with this Philistine.” 33 Saul said to David, “You are not able to go against this Philistine to fight with him; for you are just a boy, and he has been a warrior from his youth.” 34 But David said to Saul, “Your servant used to keep sheep for his father; and whenever a lion or a bear came, and took a lamb from the flock, 35 I went after it and struck it down, rescuing the lamb from its mouth; and if it turned against me, I would catch it by the jaw, strike it down, and kill it. 36 Your servant has killed both lions and bears; and this uncircumcised Philistine shall be like one of them, since he has defied the armies of the living God.” 37 David said, “The Lord, who saved me from the paw of the lion and from the paw of the bear, will save me from the hand of this Philistine.” So Saul said to David, “Go, and may the Lord be with you!”
38 Saul clothed David with his armor; he put a bronze helmet on his head and clothed him with a coat of mail. 39 David strapped Saul’s sword over the armor, and he tried in vain to walk, for he was not used to them. Then David said to Saul, “I cannot walk with these; for I am not used to them.” So David removed them. 40 Then he took his staff in his hand, and chose five smooth stones from the wadi, and put them in his shepherd’s bag, in the pouch; his sling was in his hand, and he drew near to the Philistine.