Gideon showed mixed allegiance, and faith in God was in evidence at points in his life. Abimelech was a blight in Israel’s history, showing nothing good at all. Jepththah was a tragic character—and his story, even more so.
The Jephthah narrative is relatively lengthy (compared to the accounts of, say, Tola or Abdon), so this character is clearly interesting, theologically significant, and/or memorable for the author of the account—and also to the Jews who could come later. Its dramatic force was noted by such composers as Carissimi (in a mid-17C oratorio predecessor) and Handel (in a mid-18C oratorio). Handel apparently didn’t care for the outcome of the story, though, so he changed it!
God’s changing attitudes toward the people are intriguing: first indignant (10:11-14), then influenced by affection (10:16). He does eventually see this matter through. In all, the reader perceives that Yahweh, not Jephthah or any other human, is sovereign. The narrative even labels God (a) a judge called on (b) to judge (11:27), twice using the same root as the one used for the human judges of the book.
The account of Jephthah is not glowing, by any means:
He is the son of a prostitute and is excluded by his half-brothers. (As with Hagar, Sarah’s handmaid, being driven out doesn’t keep God from paying attention.)
The Gilead elders (presumably the half-brothers) persuade Jephthah to lead them. He consents to be their ruler, and he vows to offer in sacrifice the first thing that comes out of his house when he returns victorious.
Yahweh, using Jephthah and his men, defeats the Ammonites in battle.
Jephthah’s only child, a daughter, becomes a sacrifice, and a commemorative tradition was born: Israelite girls would mourn the daughter’s fate.
In-fighting begins: a sort of civil war between Jephthah’s Gileadites and the offended Ephraimites. 42,000 of the latter were killed.
I don’t find the word “rule” or “ruler” in Judges prior to Gideon. In other words, Othniel “judged.” Deborah “judged” but was not said to have “ruled.” Each of these was said to have been “raised up by God,” but that phrase is not used of Jephthah. He is a “ruler” who appears to have arisen by human non-God-blessed initiative.
Jephthah leads for only 7 years, but his story rings through history. “Jephthah’s rash vow” and “shibboleth” have been the main takeaways, but perhaps those are not the only things to note. At this point I would ask—not because I think it’s a pleasant question or even a good question—what the reader ought to take from this story.
Are we to feel only disgust over Jephthah and over the horror of the killing of his daughter to satisfy the vow?
Or, perhaps a broader, deeper view is called for: (1) A man keeps his promises to God, period; and (2) Jephthah’s daughter, who in the story is nameless but not character-less, is a heroic figure, not a tragic one.
The daughter is pure, submissive, and faith-filled. I can imagine that her father Jephthah secretly hoped she would be mauled by wild animals while mourning in the mountains (11:37-38) so he wouldn’t have to have her killed. In the end, I suppose that, although her human life was valuable, her eternal one was more valuable, and she seems exemplary to me.