If David’s stone knocked Goliath unconscious, then he killed Goliath with his own sword when he ran over to him. He would have to run in order to get to him before he regained consciousness. Such a victory would be especially humiliating to the enemy.1
50 So 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.