Judges 11:39-40

Young's Literal Translation

³⁹ and it cometh to pass at the end of two months that she turneth back unto her father, and he doth to her his vow which he hath vowed, and she knew not a man; and it is a statute in Israel:

⁴⁰ from time to time the daughters of Israel go to talk to the daughter of Jephthah the Gileadite, four days in a year.