Midrash su Giudici 21:5

A proof of the power of excommunication is indicated by what occurred to the tribes that became incensed over what had happened to a single concubine at Gibeah but were not aroused by the idols made by Micah.⁵See Judg. 18–20. Many thousands of the tribe of Benjamin were slain on three different occasions but after they repented and prostrated themselves before the Ark, the Holy One, blessed be He, become reconciled with them? Thereupon they made a pact of excommunication, that every Israelite from the youngest to the oldest should come to the Lord (by doing good deeds), as it is said: For they made a great oath concerning him that came not unto the Lord to do good deeds, saying: He shall surely be put to death (Judg. 21:5). Though an oath was taken there, it was called a pact of excommunication to teach us that an oath and a ban of excommunication are identical. Because the men of Jabesh-Gilead did not come unto the Lord, they were sentenced to death.

Know thou the power of the ban. Come and see from the (story of) the tribes, who were zealous because of immorality against || the tribe of Benjamin. The Holy One, blessed be He, said to them: Ye are zealous because of the immorality, and ye are not zealous because of the image of Micah. Therefore the Benjamites slew some of them a first and a second and a third time, until they went before the Ark of the Covenant of the Lord seeking repentance, and they were forgiven. They decreed that all Israel should (make peace) with them, and they repented both old and young, as it is said, "For they made a great oath concerning him that came not up unto the Lord to Mizpah" (Judg. 21:5). Did all Israel take an oath? But the ban is the same as the oath.

The men of Jabesh-Gilead neither went up nor did they go with them in the assembly, and they incurred (the penalty of) death, as it is said, "Concerning him that came not up unto the Lord to Mizpah, saying, He shall surely be put to death" (ibid.).