1 Samuel 17:54

52The men of Israel and of Judah arose and shouted, and pursued the Philistines as far as Gai and to the gates of Ekron. The wounded of the Philistines fell down by the way to Shaaraim, even to Gath and to Ekron.

53The children of Israel returned from chasing after the Philistines, and they plundered their camp.

54David took the head of the Philistine and brought it to Jerusalem, but he put his armor in his tent.

55When Saul saw David go out against the Philistine, he said to Abner, the captain of the army, “Abner, whose son is this youth?” Abner said, “As your soul lives, O king, I can’t tell.”

56The king said, “Inquire whose son the young man is!”