Judges 11:35

31then it shall be, that whatever comes out of the doors of my house to meet me when I return in peace from the children of Ammon, it shall be the LORD’s, and I will offer it up for a burnt offering.”

32So Jephthah passed over to the children of Ammon to fight against them; and the LORD delivered them into his hand.

33He struck them from Aroer until you come to Minnith, even twenty cities, and to Abelcheramim, with a very great slaughter. So the children of Ammon were subdued before the children of Israel.

34Jephthah came to Mizpah to his house; and behold, his daughter came out to meet him with tambourines and with dances. She was his only child. Besides her he had neither son nor daughter.

35When he saw her, he tore his clothes, and said, “Alas, my daughter! You have brought me very low, and you are one of those who trouble me; for I have opened my mouth to the LORD, and I can’t go back.”

36She said to him, “My father, you have opened your mouth to the LORD; do to me according to that which has proceeded out of your mouth, because the LORD has taken vengeance for you on your enemies, even on the children of Ammon.”

37Then she said to her father, “Let this thing be done for me. Leave me alone two months, that I may depart and go down on the mountains, and bewail my virginity, I and my companions.”

38He said, “Go.” He sent her away for two months; and she departed, she and her companions, and mourned her virginity on the mountains.

39At the end of two months, she returned to her father, who did with her according to his vow which he had vowed. She was a virgin. It became a custom in Israel