If he answered, “No,” they told him, “Please say Shibboleth.”
A denied Ephraimite is told to say "Shibboleth." Speech becomes the means by which the Gileadites identify who belongs and who does not.
It sharpens the section's focus on tribal identity by making pronunciation a border marker.
1Then the men of Ephraim assembled and crossed the Jordan to Zaphon. They said to Jephthah, “Why have you crossed over to fight the Ammonites without calling us to go with you? We will burn your house down with you inside!” 2But Jephthah replied, “My people and I had a serious conflict with the Ammonites, and when I called, you did not save me out of their hands. 3When I saw that you would not save me, I risked my life and crossed over to the Ammonites, and the LORD delivered them into my hand. Why then have you come today to fight against me?” 4Jephthah then gathered all the men of Gilead and fought against Ephraim. And the men of Gilead struck them down because the Ephraimites had said, “You Gileadites are fugitives in Ephraim, living in the territories of Ephraim and Manasseh.” 5The Gileadites captured the fords of the Jordan leading to Ephraim, and whenever a fugitive from Ephraim would say, “Let me cross over,” the Gileadites would ask him, “Are you an Ephraimite?” 6If he answered, “No,” they told him, “Please say Shibboleth.” 7Jephthah judged Israel six years, and when he died, he was buried in one of the cities of Gilead.