Judges 12:5-6

And the Gileadites took the fords of the Jordan against the Ephraimites. And it was so, that, when any of the fugitives of Ephraim said, Let me go over, the men of Gilead said unto him, Art thou an Ephraimite? If he said, Nay; then said they unto him, Say now Shibboleth; and he said Sibboleth; for he could not frame to pronounce it right: then they laid hold on him, and slew him at the fords of the Jordan. And there fell at that time of Ephraim forty and two thousand.