Fewer Words Version: The Spirit of the Lord came upon Jephthah and he vowed a vow to the Lord, saying, "If you deliver the Ammonites into my hands, I will sacrifice to you as a burnt offering whatever comes out of my house to meet me when I return from battle."
Jephthah went to fight the Ammonites, and God delivered them into his hands. And Jephthah smote twenty Ammonite cities with a very great slaughter.
When Jephthah came home, his daughter came out to meet him with timbrels and dances. She was his only child.
When Jephthah saw her, he tore his clothes, and said, "I made a promise to God. I must keep it."
Jephthah's daughter said unto him, "If you have made a promise to God, you must keep it. God helped you slaughter the Ammonites, now you have to do what you promised you'd do. But let me do one thing first. Let me be alone for two months to go up and down on the mountains and bewail my virginity with my friends."
Jephthah said to her, "Go." And he sent her away for two months to bewail her virginity on the mountains.
At the end of two months, she returned to her father, who did what he promised God he would do. Judges 11:29-39