Bible Notes Online - Judges 21 - ESV
Commentary

v1: Israel, having defeated Benjamin in general, and Gibeah in particular, had to decide what to do next. Their oath, not to become allied in marriage with Benjamin, reflected their abhorrence of their sin.

v2-3: The result of the military victory and their oath would be that one tribe would be missing from Israel. The people rightly wept over such a situation.

v8-10: As Israel weighed up what they should do, they asked whether any Israelites had not joined the fight, to discover that Jabesh Gilead had not joined in.

v11-12: The attack on Jabesh Gilead helped to answer the problem, since 400 virgins were found in the city.

v15-19: Israel realised that the women of Jabesh Gilead were insufficient for the 600 surviving Benjamites. Again a solution presented itself. There was an annual feast at Shiloh, see 1 Sam 1.3.

v20-22: The arrangement was set, so that the Benjamites could choose brides, without the brides' fathers giving their approval. This ensured the survival of Benjamin, and did not break the oath (v1).

It seems that Benjamin remained a small tribe. Their territory was later swallowed up by Judah; see Ezra 1.5.

v25: The summary of the later events in Judges; there was no king, and the people did what pleased themselves; idolatry and immorality abounded. Chapters 17-21, which deal with Israel's internal problems, paint a sorry picture of the nation.