Albert Barnes Commentary Judges 11:36

"And she said unto him, My father, thou hast opened thy mouth unto Jehovah; do unto me according to that which hath proceeded out of thy mouth, forasmuch as Jehovah hath taken vengeance for thee on thine enemies, even on the children of Ammon." — Judges 11:36 (ASV)

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.