Judges 11:39 YLT

³⁷  And she saith unto her father, 'Let this thing be done to me; desist from me two months, and I go on, and have gone down on the hills, and I weep for my virginity -- I and my friends.'

³⁸  And he saith, 'Go;' and he sendeth her away two months, and she goeth, she and her friends, and she weepeth for her virginity on the hills;

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.