John Calvin on Numbers 30:5-8

5. But if her father disallow her. The expression is remarkable, “And the Lord shall forgive her,” whereby Moses gently reproves the foolish thoughtlessness of the girl; and soon afterwards the same thing is spoken of married women. And surely their rashness is worthy of reprehension, if unmindful of their condition, they, as it were, shake off the yoke and hastily commit themselves. God therefore hints that they are not without blame; but lest they should be tormented by secret remorse, He removes every scruple, declaring that He will forgive, if the performance of the vow shall have been prevented in any other quarter. When the dissent of the father or the husband is required on the same day, it is tantamount to saying that what they have once approved of cannot be disallowed. Further, to “hold his peace” to a wife or daughter, signifies that he does not oppose, but give by silence a token of consent.