Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
The history of Jephthah appears to be an independent history inserted by the compiler of the Book of Judges. Jdg 11:4-5 introduce the Ammonite war without any apparent reference to Jdg 10:17-18.
A genealogy of Manasseh Ch1 7:14-17 gives the families which sprang from Gilead, and among them mention is made of an "Aramitess" concubine as the mother of one family. Jephthah, the son of Gilead by a strange woman, fled, after his father's death, to the land of Tob Jdg 11:3, presumably the land of his maternal ancestors (compare Jdg 9:1) and an "Aramean" settlement (Sa2 10:6, Sa2 10:8; 1 Macc. 5:13). It is difficult to conceive that Jephthah was literally the son of Gilead, if Gilead was the son of Machir, the son of Manasseh. Possibly "Gilead" here denotes the heir of Gilead, the head of the family, whose individual name has not been preserved, nor the time when he lived.
The land of Tob - To the north of Gilead, toward Damascus. The readiness with which Jephthah took to the freebooter's life gives us a lively picture of the unsettled times in which he lived.
This gives a wider signification to Jdg 11:2-3, and shows that Jephthah's "brethren" include his fellow tribesmen.
Jephthah made his own aggrandisement the condition of his delivering; his country. The circumstances of his birth and long residence in a pagan land were little favorable to the formation of the highest type of character. Yet he has his record among the faithful Heb 11:32.
Jephthah uttered all his words before the Lord in Mizpeh - This phrase designates the presence of the tabernacle, or the ark, or of the high priest with Urim and Thummim Jdg 20:26; Jdg 21:2; Jos 18:8; Sa1 21:7. The high priest waited upon Jephthah with the ephod, and possibly the ark, at his own house (see Jdg 20:18 here). A trace of Jephthah's claim to unite all Israel under his dominion is found in Jdg 12:2, and breathes through his whole message to the king of the Ammonites. See Jdg 11:12, Jdg 11:15, Jdg 11:23, Jdg 11:27.
From Arnon even unto Jabbok ... - The land bounded by the Arnon on the south, by the Jabbok on the north, by the Jordan on the west, and by the wilderness on the east was, of old, the kingdom of Sihon, but then the territory of Reuben and Gad.
Consult the marginal references. If the ark with the copy of the Law Deu 31:26 was at Mizpeh, it would account for Jephthah's accurate knowledge of it; and this exact agreement of his message with Numbers and Deuteronomy would give additional force to the expression, "he uttered all his words before the Lord" Jdg 11:11.
No mention is made of this embassy to Moab in the Pentateuch.
Into my place - This expression implies that the trans-Jordanic possessions of Israel were not included in the land of Canaan properly speaking.
The title "God of Israel" has a special emphasis here, and in Jdg 11:23. in a narrative of transactions relating to the pagan and their gods.
Chemosh was the national god of the Moabites (see the marginal references); and as the territory in question was Moabitish territory before the Amorites took it from "the people of Chemosh," this may account for the mention of Chemosh here rather than of Moloch, or Milcom, the god of the Ammonites. Possibly the king of the children of Ammon at this time may have been a Moabite.
Jephthah advances another historical argument. Balak, the king of Moab, never disputed the possession of Sihon's kingdom with Israel.
Then the Spirit of the Lord ... - This was the sanctification of Jephthah for his office of Judge and savior of God's people Israel. Compare Jdg 6:34; Jdg 13:25. The declaration is one of the distinctive marks which stamp this history as a divine history.
The geography is rather obscure, but the sense seems to be that Jephthah first raised all the inhabitants of Mount Gilead; then he crossed the Jabbok into Manasseh, and raised them; then he returned at the head of his new forces to his own camp at Mizpeh to join the troops he had left there; and thence at the head of the whole army marched against the Ammonites, who occupied the southern parts of Gilead.
The words of this verse prove conclusively that Jephthah intended his vow to apply to human beings, not animals: for only one of his household could be expected to come forth from the door of his house to meet him. They also preclude any other meaning than that Jephthah contemplated a human sacrifice. This need not, however, surprise us, when we recollect his Syrian birth and long residence in a Syrian city, where such fierce rites were probably common. The Syrians and Phoenicians were conspicuous among the ancient pagan nations for human sacrifices, and the transfer, under such circumstances, to Yahweh of the rites with which the false gods were honored, is just what one might expect. The circumstance of the Spirit of the Lord coming on Jephthah Jdg 11:29 is no difficulty; as it by no means follows that because the Spirit of God endued him with supernatural valor and energy for vanquishing the Ammonites, He therefore also endued him with spiritual knowledge and wisdom. The Spirit of the Lord came upon Gideon, but that did not prevent his erring in the matter of the ephod Jdg 8:27. Compare Co1 12:4-11; Gal 2:11-14.
As in the conflicts with the Moabites, Canaanites, and Midianites Judg. 3; 4; 7, the battle was on Israelite territory, in self-defense, not in aggressive warfare.
The plain of the vineyards - Rather, "Abel-Ceramim" (compare Abel-Meholah), identified with an "Abel" situated among vineyards, 7 miles from Robbah. "Minnith" is "Maanith," 4 miles from Heshbon, on the road to Rab-bah.
His daughter came out to meet him - The precise phrase of his vow Jdg 11:31. She was his "only child," a term of special endearment (see Jer 6:26; Zac 12:10). The same word is used of Isaac Gen 22:2, Gen 22:12, Gen 22:16.
Jephthah was right in not being deterred from keeping his vow by the loss and sorrow to himself (compare the marginal references), just as Abraham was right in not withholding his son, his only son, from God, when commanded to offer him up as a burnt-offering. But Jephthah was wholly wrong in that conception of the character of God which led to his making the rash vow. And he would have done right not to slay his child, though the guilt of making and of breaking such a vow would have remained. Josephus well characterizes the sacrifice as "neither sanctioned by the Mosaic law, nor acceptable to God."
The touching submission of Jephthah's daughter to an inevitable fate shows how deeply-rooted at that time was the pagan notion of the propriety of human sacrifice.
Bewail my virginity - To become a wife and a mother was the end of existence to an Israelite maiden. The premature death of Jephthah's daughter was about to frustrate this end.
There is no allusion extant elsewhere to this annual lamentation of the untimely fate of Jephthah's daughter. But the poetical turn of the narrative suggests that it may be taken from some ancient song (compare the marginal note 4).