Zeal for Immorality but Silence Toward the Idol of Micah

Know the power of the ban [cherem]. Come and see: from the tribes that were zealous over the immorality of the tribe of Benjamin, the Holy One, blessed be He, said to them: You were zealous over the immorality, yet you were not zealous over the idol of Micah. And because their zeal was not over the idol of Micah, therefore the Benjaminites slew among them a first time and a second time, until they fell before the Ark of the Covenant of the LORD and sought to repent, and the Holy One, blessed be He, was reconciled to them. And they imposed a ban that all Israel should follow them, from the least to the greatest, as it is said, "For the great oath had been taken" (Judges 21:5). Now was it a great oath that all Israel had sworn? Rather, it is to teach you that the ban is the oath: "that whoever did not come up to the LORD at Mizpah, saying, He shall surely be put to death" (Judges 21:5).