Judges 21:5

21:5 The Israelites asked, “Who from all the Israelite tribes has not assembled before the Lord?” They had made a solemn oath that whoever did not assemble before the Lord at Mizpah must certainly be executed.

Judges 21:11

21:11 Do this: exterminate every male, as well as every woman who has had sexual relations with a male. But spare the lives of any virgins.” So they did as instructed.

Judges 21:18

21:18 But we can’t allow our daughters to marry them, for the Israelites took an oath, saying, ‘Whoever gives a woman to a Benjaminite will be destroyed!’