Questions like the following could be asked: Why did God not prevent Jephthah from making his vow? Or why did he not remind Jephthah afterwards that he did not absolutely have to fulfil it and thus increase his sin? Why did God not remind Jephthah that obedience was better than sacrifice? In Leviticus 1, only male herd or flock animals or certain clean birds are acceptable to God as burnt offerings. And there are prohibitions in Scripture of child sacrifice: Deuteronomy 18:9–10 speaks of ritually passing a son or daughter through fire is a strictly prohibited abomination; see also Leviticus 18:21, Leviticus 20:1–5, Deuteronomy 12:31, 2 Kings 16:3, 2 Kings 21:6. Why did God not speak to Jephthah and stop him as he had stopped Abraham before he could slay his child (see Genesis 22:10–12)?
We are not told the answer to these questions. Was Jephthah truly ignorant of God’s law? His earlier reciting of Israelite history to the Ammonite king (Judges 11:14–27) would suggest he had sufficient access to, if not also awareness of, his own history to know that God prohibited human sacrifice.
We can say that the Lord allowed Jephthah, in his ignorance of God’s law, to reap the fruit of his vow, a vow that flowed from his horribly distorted view of God and therefore what pleases God. Ideas have consequences; sinful ideas can have bad consequences. And our Lord is a God who won’t always prevent us from suffering the consequences of our sins, even when those sins hurt our loved ones.
39 And at the end of two months, she returned to her father, who did with her according to his vow that he had made. She had never known a man, and it became a custom in Israel