Notice the trigger words in this quote from 2007:
*** w07 5/15 pp. 9-10 Jephthah Keeps His Vow to Jehovah ***Is Jephthah really going to sacrifice his daughter? No. That cannot be what he has in mind. Jehovah detests literal human sacrifice, one of the wicked practices of the Canaanites. (Leviticus 18:21; Deuteronomy 12:31) Not only was God’s spirit acting upon Jephthah when he made his vow but Jehovah also blessed his endeavors. The Scriptures speak well of Jephthah for his faith and for the role he played in connection with the divine purpose. (1 Samuel 12:11; Hebrews 11:32-34) So a human sacrifice—a murder—is completely out of the question. What, then, was Jephthah thinking when he vowed to offer a person to Jehovah?
Jephthah evidently meant that he would devote the one whom he met to the exclusive service of God. The Mosaic Law provided for the vowing of souls to Jehovah. For instance, women served at the sanctuary, perhaps drawing water. (Exodus 38:8; 1 Samuel 2:22) Little is known about such service or even whether it was usually permanent. Jephthah apparently had such special devotion in mind when making his vow, and it seems that his promise implied permanent service.
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I always thought long about this. The bible doesn't even give her name which is frequent in the bible: Noah's wife. her daughters-in-laws...
(Judges 11:30-31) . . .Then Jeph´thah made a vow to Jehovah and said: "If you without fail give the sons of Am´mon into my hand, 31 it must also occur that the one coming out, who comes out of the doors of my house to meet me when I return in peace from the sons of Am´mon, must also become Jehovah’s, and I must offer that one up as a burnt offering."
Notice more trigger points
*** w66 7/1 pp. 413-414 Judge Jephthah and His Vow ***Moreover, we have seen how he kept taking notice of Jehovah. This quality helps us to understand why he made this vow. Why? No doubt because he had such a great desire that Jehovah’s cause be victorious that he was willing to sacrifice anything for it, be what it may. Jehovah certainly was very real to him! Besides, do we not read that ‘Jehovah’s spirit came upon Jephthah’ shortly before he made this vow? It is therefore reasonable to conclude that what Jephthah vowed was entirely in harmony with God’s holy spirit.
It, therefore, does not seem reasonable to conclude that Jephthah intended to offer up literally whoever came out to meet him as a burnt offering. Such a course would go against God’s law about the sanctity of human life and would be the only instance in the whole Bible where a human was actually sacrificed by another person who had God’s approval. Rather, it seems reasonable to conclude that what Jephthah intended, and what he did, was that whoever came out to meet him was to be dedicated to God’s service and that he used the expression "burnt offering" merely as a figure of speech.—Gen. 9:6.
He could not have thought that some animal would come out to meet him, as some claim, for he said that "the one coming out . . . of the doors of my house to meet me" he would offer up, and the Israelites did not keep lower animals in their houses—not even dogs, which some people today keep as pets! So he must have had in mind either a servant or a relative and that it might even be his only child, his beloved daughter. But regardless of the cost, he was willing to pay it if Jehovah would only grant him the victory!
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Who really paid the cost? His daugher. She was said to be his only child...but Jewish men could marry several women and could have children far into old age. So what was his loss; after all women couldn't inherit anything.
Would it be any different for God to look past this when he later looked past David's adultery with Bath-sheba and arranging the murder of her husband. David and Bathsheba both should have been put to death under the Law but were not. God's holy spirit was said to continue on David after that. Who was punished, David's wives and family were, the child died but they continued to live. There was no provision for "mercy" under the Law. Why could not the same God who did this, look past what Jephthah did?