Judges 12:4-6

4Jephthah brought together all the men of Gilead. They fought against the men of Ephraim's tribe. The men of Gilead won the fight. They were angry because the men of Ephraim had insulted them. They had said, ‘You people of Gilead have run away to live on the land of Ephraim and Manasseh.’

5After that, Gilead's army put guards at the places where people could go across the Jordan River. They wanted to stop people from Ephraim going across the river. If one of Ephraim's soldiers was trying to escape, they would ask him, ‘Do you belong to Ephraim's tribe?’ The man would say, ‘No, I do not!’

6Then they would tell him, ‘Say, “Shibboleth!” ’ People from Ephraim could not say that word properly. So if the man said, ‘Sibboleth,’ they would take hold of him and kill him. That day, they killed 42,000 soldiers of Ephraim at those places on the Jordan River.