Judges 12:4-6

4Then Jephthah assembled all the men of Gilead and fought with [the tribe of] Ephraim; and the men of Gilead defeated Ephraim, because they had said, “You Gileadites are fugitives of Ephraim, in the midst of [the tribes of] Ephraim and Manasseh.”

5And the Gileadites took the fords of the Jordan opposite the Ephraimites; and when any of the fugitives of Ephraim said, “Let me cross over,” the men of Gilead would say to him, “Are you an Ephraimite?” If he said, “No,”

6they said to him, “Then say ‘Shibboleth.’ ” And he said, “Sibboleth,” for he could not pronounce it correctly. Then they seized him and killed him at the fords of the Jordan. At that time forty-two thousand of the Ephraimites fell.