Commentaire sur Les Nombres 30:6

ואם הניא אביה אתה BUT IF HER FATHER DISALLOWED HER — The Hebrew signifies, “if he withholds her” from the vow, that is to say, that he annuls it for her. I would not know what this expression הניא, “withholding”, implies (i.e., how he withholds her) — but when it states, (v. 9) “But if on the day that he hears, he withholds her and annuls [her vows]”, one must admit that “the withholding” consists in “annulling the vow” (i.e. in exclaiming מופר לך) (Sifrei Bamidbar 153:6). But still the plain meaning is that it is a term for “withholding” and “removing” (and the word והפר only shows how and by what means she is to be withheld from keeping her vow); and similar is (Numbers 32:7): “And wherefore do you remove (תניאון) [the heart of the children of Israel from the idea of passing over the land]”; and so, too, (Psalms 141:5): “Oil so choice, let not my head turn away (יניא), and similar, also, (Numbers 14:34): “And ye shall know My turning aside (תנואתי)” — i.e. ye shall know that ye have turned aside from Me.

וה' יסלח לה, for having made a vow which it was not in her power to fulfill

וה' יסלח לה כי הניא אביה אותה, “and Hashem will forgive her for her father had restrained her.” The message of this verse is that G’d will forgive her only any violation committed after her father had restrained her. If the girl in question had pre-empted her father’s objection and violated her vow already, she will not be forgiven. The reason is that the father’s authority does not extend to revoking a vow retroactively, that is a privilege the Torah gave only to judges.