Judges 11:34-40

When Jephthah came to his house at Mizpah, behold, his daughter was coming out to meet him with tambourines and with dancing. Now she was his one and only child; besides her he had no son or daughter. When he saw her, he tore his clothes and said, “Alas, my daughter! You have brought me very low, and you are among those who trouble me; for I have given my word to the LORD, and I cannot take it back.” So she said to him, “My father, you have given your word to the LORD; do to me as you have said, since the LORD has avenged you of your enemies, the sons of Ammon.” She said to her father, “Let this thing be done for me; let me alone two months, that I may go to the mountains and weep because of my virginity, I and my companions.” Then he said, “Go.” So he sent her away for two months; and she left with her companions, and wept on the mountains because of her virginity. At the end of two months she returned to her father, who did to her according to the vow which he had made; and she had no relations with a man. Thus it became a custom in Israel, that the daughters of Israel went yearly to commemorate the daughter of Jephthah the Gileadite four days in the year.