Judges 12:4-6

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?”

If he answered, “No,” 6they told him, “Please say Shibboleth.”

If he said, “Sibboleth,” because he could not pronounce it correctly, they seized him and killed him at the fords of the Jordan. So at that time 42,000 Ephraimites were killed.