1 Samuel 17:34-40

But David said to Saul, “Your servant was tending his father’s sheep. When a lion or a bear came and took a lamb out of the flock, I went out after it and attacked it and rescued the lamb from its mouth; and when it rose up against me, I seized it by its whiskers and struck and killed it. Your servant has killed both the lion and the bear; and this uncircumcised Philistine will be like one of them, since he has taunted and defied the armies of the living God.” David said, “The LORD who rescued me from the paw of the lion and from the paw of the bear, He will rescue me from the hand of this Philistine.” And Saul said to David, “Go, and may the LORD be with you.” Then Saul dressed David in his garments and put a bronze helmet on his head, and put a coat of mail (armor) on him. Then David fastened his sword over his armor and tried to walk, [but he could not,] because he was not used to them. And David said to Saul, “I cannot go with these, because I am not used to them.” So David took them off. Then he took his [shepherd’s] staff in his hand and chose for himself five smooth stones out of the stream bed, and put them in his shepherd’s bag which he had, that is, in his shepherd’s pouch. With his sling in his hand, he approached the Philistine.