Judges 11:29-40 - Jephthah Makes A Vow
29 Then the Spirit of the LORD came upon Jephthah, and he passed through Gilead and Manas'seh, and passed on to Mizpah of Gilead, and from Mizpah of Gilead he passed on to the Ammonites. 30 And Jephthah made a vow to the LORD, and said, "If thou wilt give the Ammonites into my hand, 31 then whoever comes forth from the doors of my house to meet me, when I return victorious from the Ammonites, shall be the LORD's, and I will offer him up for a burnt offering."
32 So Jephthah crossed over to the Ammonites to fight against them; and the LORD gave them into his hand. 33 And he smote them from Aro'er to the neighborhood of Minnith, twenty cities, and as far as Abel-keramim, with a very great slaughter. So the Ammonites were subdued before the people of Israel.
34 Then Jephthah came to his home at Mizpah; and behold, his daughter came out to meet him with timbrels and with dances; she was his only child; beside her he had neither son nor daughter. 35 And when he saw her, he rent his clothes, and said, "Alas, my daughter! you have brought me very low, and you have become the cause of great trouble to me; for I have opened my mouth to the LORD, and I cannot take back my vow."
36 And she said to him, "My father, if you have opened your mouth to the LORD, do to me according to what has gone forth from your mouth, now that the LORD has avenged you on your enemies, on the Ammonites." 37 And she said to her father, "Let this thing be done for me; let me alone two months, that I may go and wander on the mountains, and bewail my virginity, I and my companions."
38 And he said, "Go." And he sent her away for two months; and she departed, she and her companions, and bewailed her virginity upon the mountains. 39 And at the end of two months, she returned to her father, who did with her according to his vow which he had made. She had never known a man. And it became a custom in Israel 40 that the daughters of Israel went year by year to lament the daughter of Jephthah the Gileadite four days in the year.