Judges 19 is a fairly gruesome chapter so it is worth noting that this story is included not as recommended behaviour but as a historical explanation for the events that take place in Judges 20. No-one in this chapter comes out in a good light.
It is not clear why this Levite was travelling or where his home town was. He takes a concubine (v1), which would imply that he had a wife and/or that she was a slave. She commits adultery (v2) but he seeks her out and tries to convince her to come back with him. She takes him to her father’s house and her father persists in trying to make the man stay in Bethlehem. This might imply that the father was poor (perhaps he had sold his daughter) and that he wanted the Levite to stay indefinitely. In any case, the Levite is delayed in departed with his concubine, so they do not get far on their journey before they have to stop for the night. This is context for the events to follow.
The Levite and his concubine stop at Gibeah, specifically choosing not to stop at Jebus because it is a foreign city. The citizens of Gibeah should have been welcoming. Instead certain of the men try to gang-rape the man — a truly awful crime. The fact that the man offers them his beloved concubine instead, either demonstrates his own fear or his own revulsion at their intentions. Given that, by the end of the story, all Israel is enraged by the gang-rape of the concubine it seems that fear is the more likely. There is no suggestion here that raping concubines was considered to be acceptable behaviour (it wasn’t).
The Levite had saved his own skin but his concubine has been killed. Outraged by this crime, he divides her body and sends the parts to all the tribes of Israel as a graphic message to draw them to battle.
It is difficult to draw positive conclusions from this chapter. The concubine was not faithful to her husband, but that does not excuse the Levite’s actions. I think we can only conclude that the Levite offered up his concubine because he was terrified of the men that came to rape him. The crime of the men is Gibeah is awful and invokes the outrage of all Israel.