Judges 21:4
And it came to pass on the morrow, that the people rose early, and built there an altar, and offered burnt offerings and peace offerings. And it came to pass on the morrow, that the people rose early, and built there an altar, and offered burnt offerings and peace offerings.
The closing chapters of Judges, chapters 17 through 21, stand at the end of the book but belong to the early part of the history of the judges, whose real story ends with chapter 16. The altar built and the burnt offerings and peace offerings made on the morrow belong to that out-of-place section. They belong to a pitiful record of backsliding that brought disgrace and punishment on Israel.
That backsliding showed a time when conventional hospitality was valued above female virtue and when clannish loyalty to a tribe was valued above the rendering of justice. That same pattern of misplaced loyalty and corrupted values is still seen today. Israel's backsliding in it never gives an excuse for sin. It does not mean anyone can backslide without punishment.