The men of Israel and of Judah arose, and shouted, and pursued the Philistines, until you come to 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.
Another possibility is that Saul’s words could have been an idiom for, "What is his background?" Perhaps the writer included this reference to David’s family in the text because David’s trust and obedience resulted in his family enjoying special blessings from God through Saul. 1 Samuel 17:55-58 focus on the question of whose son David was. This event proved that David was a true son of God who had the reputation and interests of his Father and his Father’s people at heart (cf. John 8:29).