Judges 12:6

then said they unto him, Say now shibboleth (stream, flood); and he said Sibboleth; for he could not frame (was not able) to pronounce it right. It was a difference in dialect, and the Ephraimites simply could not get the sound right; their pronunciation betrayed them. Then they took him, every Ephraimite who was thus exposed, and slew him at the passages of Jordan; and there fell at that time, in the entire campaign, of the Ephraimites forty and two thousand. Thus the rebellious arrogance of Ephraim was punished.