Judges 12:6

12:6 then they said to him, “Say ‘Shibboleth!’ ”17 If he said, “Sibboleth” (and could not pronounce the word18 correctly), they grabbed him and executed him right there at the fords of the Jordan. On that day forty-two thousand Ephraimites fell dead.

17	sn The inability of the Ephraimites to pronounce the word shibboleth the way the Gileadites did served as an identifying test. It illustrates that during this period there were differences in pronunciation between the tribes. The Hebrew word shibboleth itself means “stream” or “flood,” and was apparently chosen simply as a test case without regard to its meaning.
18	tn Heb “and could not prepare to speak.” The precise meaning of יָכִין (yakhin) is unclear. Some understand it to mean “was not careful [to say it correctly]”; others emend to יָכֹל (yakhol, “was not able [to say it correctly]”) or יָבִין (yavin, “did not understand [that he should say it correctly]”), which is read by a few Hebrew mss.