What does 1 Samuel 17:58 mean?

Although King Saul knew David (1 Samuel 16:14–23; 17:31–40), he did not recall whose son David was (1 Samuel 17:55). Now David returns to the king, this time carrying the freshly severed head of the Philistine champion after bringing the giant down with a sling and a stone (1 Samuel 17:48–51, 57).

Saul asks David about his father directly. He calls David "young man," showing once again just how young David must have been when he killed Goliath (1 Samuel 17:33). He was old enough to be an honorary armor-bearer (1 Samuel 16:21), but young enough to be expected to watch his father's sheep instead of going to battle with the Philistines (1 Samuel 17:15).

David tells the king that his father is Jesse of Bethlehem. When David first enters the narrative of this chapter, he is introduced as "the son of an Ephrathite of Bethlehem in Judah, named Jesse" (1 Samuel 17:12). David came to the battle that morning because his father sent him with a load of provisions for his brothers (1 Samuel 17:17–20). The young man could not know that the Lord would use that seemingly mundane errand to bring David to the field of battle. There, his boldness and confidence in the Lord would bring him to a fight to the death with Goliath. Now he stood before Israel's king with the head of Israel's greatest enemy in his hands.

Saul seems to have wanted to know the name of David's father so he could take David into his permanent service (1 Samuel 18:2). David's days of watching his father's sheep had likely ended. Saul, or his administrators, would also need to know which household to reward (1 Samuel 17:25).