Matthew Poole and continuators on Numbers 30:5

5 But if her Father disallow her in the day that he heareth ; not any of her vows, or of her bonds, wherewith she hath bound her soul, shall stand: and the LORD shall forgive her : because her Father disallowed her.

i. e. Speedily, or without delay, allowing onely necessary and convenient time for deliberation. And it is hereby intimated that the day or time he had for disallowing her vow, was not to be reckoned from her vowing, but from his hearing, or knowledge of her vow

Or will forgive either her rashness of making such vows, or rather her not performing of it. But this is to be understood only of such vows which could not be performed without invading the Fathers, or Superiours right; for if one should vow to forbear such, or such a sin, and all unnecessary occasions or means leading to it, and to perform such, or such duties, when he had opportunity, no Father, nor Superiour can discharge him from such vows.