Albert Barnes Commentary 1 Samuel 17:51

"Then David ran, and stood over the Philistine, and took his sword, and drew it out of the sheath thereof, and slew him, and cut off his head therewith. And when the Philistines saw that their champion was dead, they fled." — 1 Samuel 17:51 (ASV)

Champion - This is a different word from the one translated this way in 1 Samuel 17:4 and 1 Samuel 17:23; a better translation is “warrior.”