Judges 11:28-38

28 However the king of the children of Ammon hearkened not unto the words of Jephthah which he sent him.
29 Then the Spirit of the LORD came upon Jephthah, and he passed over Gilead and Manasseh, and passed over Mizpah of Gilead; and from Mizpah of Gilead he passed over unto the children of Ammon.
30 And Jephthah vowed a vow unto the LORD, and said, "If Thou shalt without fail deliver the children of Ammon into mine hands,
31 then it shall be that whatsoever cometh forth from the doors of my house to meet me, when I return in peace from the children of Ammon, shall surely be the LORD'S, and I will offer it up for a burnt offering."
32 So Jephthah passed over unto the children of Ammon to fight against them, and the LORD delivered them into his hands.
33 And he smote them from Aroer even till thou come to Minnith, even twenty cities, and unto the plain of the vineyards with a very great slaughter. Thus the children of Ammon were subdued before the children of Israel.
34 And Jephthah came to Mizpah unto his house, and behold, his daughter came out to meet him with timbrels and with dances; and she was his only child. Besides her he had neither son nor daughter.
35 And it came to pass, when he saw her, that he rent his clothes 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 unto the LORD, and I cannot go back."
36 And she said unto him, "My father, if thou hast opened thy mouth unto the LORD, do to me according to that which hath proceeded out of thy mouth, forasmuch as the LORD hath taken vengeance for thee on thine enemies, even of the children of Ammon."
37 And she said unto her father, "Let this thing be done for me: let me alone two months, that I may go up and down upon the mountains and bewail my virginity, I and my fellows."
38 And he said, "Go." And he sent her away for two months; and she went with her companions, and bewailed her virginity upon the mountains.