The sentence, further, was that none of the people of the ancestors should give his daughter in marriage to [members of Benjamin’s tribe]. This was confirmed by a solemn oath. But relenting at having laid so hard a sentence on their brothers, they moderated their severity so as to give them in marriage those maidens that had lost their parents, whose fathers had been slain for their sins, or to give them the means of finding a wife by a raid. Because of the villainy of so foul a deed, they who had violated another’s marriage rights were shown to be unworthy to ask for marriage. But for fear that one tribe might perish from the people, they connived at the deceit.
[AD 397] Ambrose of Milan on Judges 21:17-21