I think you must be referring to Jephthah, and the narrative of Judges 11. That was recently discussed a little on
this thread.
Obviously, if Jephthah did not offer a human sacrifice that would ease the dilemma. And that is the approach I take. Obviously many others have disagreed with that, but I notice in Judges 11:
1. that Jephthah is quite familiar with the Old Testament.
2. that Jephthah's daughter wants to bewail her virginity, not her life.
3. that Jephthah's vow gives God the choice of what He wants from Jephthah's house, and it taxes my credulity that God chose for Jephthah to slaughter his daughter.
4. that his daughter seems to have had a good upbringing and to have learned the fear of God.
5. I notice that in Numbers the Levites are spoken of as offered to the Lord (not as a burnt offering, I am aware, but it does show that the sacrificial language can be applied to those who are devoted to God's service). Then I ask myself the question, what if a donkey had come forth? You couldn't offer those on an altar, but they could be given for service.
6. I notice that Jephthah is mentioned in Hebrews 11 as a good example of faith.
And with all of that put together, I conclude that the vow was almost certainly rash, and that Jephthah was far from perfect; but that he would kill his blameless daughter as an offering to the Lord is an unwarranted conclusion from the text. Jephthah illustrates
Psalm 15:4
and
Ecclesiastes 5:4,5
. The law of charity should govern Scripture interpretation as well as human interaction, and we should be careful of accusing any saint in Scripture of sin beyond the requirements of the text. Obviously, from Jephthah's reaction he did not want to follow through with his vow, and so in that sense it can clearly be called a rash vow; but he didn't withhold his daughter, his only daughter whom he loved, in order to pay what he had vowed.