John Gill Commentary Judges 20:6

"And I took my concubine, and cut her in pieces, and sent her throughout all the country of the inheritance of Israel; for they have committed lewdness and folly in Israel." — Judges 20:6 (ASV)

And I took my concubine, and cut her in pieces
Lest it should be thought that these barbarous creatures, after they had used her in such a manner that occasioned her death, that they had committed this fact also; the Levite takes it to himself, and owns that he did that:

and sent her throughout all the country of the inheritance of Israel ;
to alarm them, and excite their attention to what had passed, and to raise their indignation against it:

for they have committed lewdness and folly in Israel ;
being guilty of adultery and murder, and would have committed the unnatural crime, if they could have had an opportunity of doing it.