Judges 11:30-40

30And Jephthah vowed a vow to Jehovah, and said, If thou wilt without fail give the children of Ammon into my hand, 31then shall that which cometh forth from the door of my house to meet me, when I return in peace from the children of Ammon, be Jehovah's, and I will offer it up for a burnt-offering. 32And Jephthah passed over to the children of Ammon to fight against them; and Jehovah gave them into his hand. 33And he smote them from Aroer until thou come to Minnith, twenty cities, even unto Abel-Cheramim, with a very great slaughter; and the children of Ammon were subdued before the children of Israel. 34And Jephthah came to Mizpah to his house, and behold, his daughter came out to meet him with tambours and with dances; and she was an only child: besides her he had neither son nor daughter. 35And it came to pass, when he saw her, that he rent his garments, and said, Alas, my daughter! thou hast brought me very low, and thou art one of them that trouble me; for I have opened my mouth to Jehovah, and I cannot go back. 36And she said to him, My father, if thou hast opened thy mouth to Jehovah, do to me according to that which has proceeded out of thy mouth; forasmuch as Jehovah has taken vengeance for thee upon thine enemies, upon the children of Ammon. 37And she said to her father, Let this thing be done for me: leave me alone two months, that I may go and descend to the mountains, and bewail my virginity, I and my companions. 38And he said, Go. And he sent her away for two months. And she went with her companions, and bewailed her virginity upon the mountains. 39And it came to pass at the end of two months, that she returned to her father, and he performed on her the vow that he had vowed; and she had known no man. And it became a fixed custom in Israel, 40that from year to year the daughters of Israel go to celebrate the daughter of Jephthah the Gileadite four days in the year.