Shofetim 12:5-6

And the Gilead took the fords of the Yarden before the Ephrayim; and it was so, that when those Ephrayim which were escaped said, Let me cross over; that the anshei Gil'ad said unto him, Art thou an Ephrati? If he said, No, Then said they unto him, Say now Shibbolet; and he said Sibbolet, for he could not pronounce it right. Then they took him, and slaughtered him at the fords of the Yarden; and there fell at that time of the Ephrayim forty and two thousand.