37 And she said unto her father, Let this thing be done for me: let me alone two months, that I may go up and down upon the mountains, and bewail my virginity, I and my fellows.
[AD 253] Origen of Alexandria on Judges 11:34-38
The remaining sacrifices, of which those relating to the law are a symbol, are akin to this sacrifice. But in addition, the other sacrifices akin to this sacrifice seem to me to be the shedding of the blood of the noble martyrs. It was not in vain that the disciple John saw them standing beside the heavenly altar. “But who is wise, that he shall understand these things? Or intelligent, and he shall know them?”3Now comprehend, even if to a limited extent, the more spiritual sense of such sacrifices which cleanse those for whom they are offered; one must understand the sense of the sacrifice of the daughter of Jephthah who was offered as a burnt offering because of the vow of him who conquered the children of Ammon. She who was offered as a burnt offering consented to this vow, for, when her father said, “I have opened my mouth to the Lord against you,” she said to him, “And if you have opened your mouth to the Lord against me, perform your vow.”
Such accounts give an appearance of great cruelty to God to whom such sacrifices are offered for humanity’s salvation. We need a generous and perceptive spirit in order to refute the reproaches made against providence and, at the same time, to make a defense of all the sacrifices insofar as they are rather mysterious and beyond human nature.

[AD 430] Augustine of Hippo on Judges 11:34-38
The Scriptures do not seem to pass judgment on this vow and its fulfillment as it does quite clearly in the case of Abraham, when he was ordered to sacrifice his son and did so. Rather the Scriptures seem to have only recorded the matter and left it to the reader to evaluate, just as in the case of Judah, Jacob’s son, who in ignorance lay with his daughter-in-law but committed fornication by the very act, because he thought her to be a prostitute. The Scriptures never approve nor disapprove of the act explicitly but let the matter stand, to be evaluated and contemplated after consulting the righteousness and law of God. Therefore, the Scriptures of God do not offer any comment in either the vow or its fulfillment, so that our mind might be put to work to pass judgment on this matter and so that we might now say that such a vow displeased God and led to the punishment that his only daughter, of all people, ran out to meet her father.

[AD 1781] Richard Challoner on Judges 11:37
Bewail my virginity: The bearing of children was much coveted under the Old Testament, when women might hope that from some child of theirs, the Saviour of the world might one day spring. But under the New Testament virginity is preferred. 1 Cor. 7. 35.