Numbers 30:5 - Wesley's Explanatory Notes

In the days — Speedily, or without delay, allowing only 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 knowledge of her vow. The Lord shall forgive — Or, will forgive her not performing it. But this should be understood only of vows which could not be performed without invading the father's right; for if one should vow to forbear such, or such a sin, and all occasions or means leading to it, and to perform such, or such duties, when he had opportunity, no father can discharge him from such vows. If this law does not extend to children's marrying without the parent's consent, so far as to put it in the power of the parent, to disannul the marriage, (which some think it does) yet certainly it proves the sinfulness of such marriages, and obliges those children to repent and humble themselves before God and their parents.