Numbers 30:4

בבית אביה [IF A WOMAN VOW] … BEING IN HER FATHER’S HOUSE — i.e., under her father’s control, but the law here stated applies even though she be not in his house, provided she be under his control (Sifrei Bamidbar 153:4). בנעורה IN HER YOUTH — when she is a נערה i.e., in the first state of womanhood, but not when she is a קטנה, a minor, and not when she is a בוגרת (in full womanhood); for so far as a minor is concerned, her vow is in general no vow (it is null and void ab initio), and a בוגרת is not under her father’s control so that he can annul her vows. What is a קטנה, a minor, in respect to vows? We may gather this from what our Rabbis said: a woman of eleven years and one day must have her vows investigated until she reaches the age of twelve years; if she understands in Whose name it is that she has made the vow or in Whose name it is she has dedicated the thing, her vow is a vow, but a woman of twelve years and a day does not require any investigation regarding her vow (Niddah 56b).

וְאִשָּׁ֕ה כִּֽי־תִדֹּ֥ר נֶ֖דֶר לַיהֹוָ֑ה וְאָסְרָ֥ה אִסָּ֛ר בְּבֵ֥ית אָבִ֖יהָ בִּנְעֻרֶֽיהָ׃

If a woman also vow a vow to the Lord, and bind herself by a bond, being in her father’s house in her youth;