2,836. A Mistake in Annulling a Vow

Hilchos Nedarim 12:20

If a father or husband heard of a vow and remained silent because he was unaware that he had the power to annul it, or he knew that he had such an ability but was unaware that this vow required annulling, then he can annul the vow when he learns this. Learning that he can/must annul this vow is tantamount to learning of the vow itself, so he can annul it that entire day.

Hilchos Nedarim 12:21

An erroneous annulment must done again. Examples include: if a man annulled his wife’s vow thinking she was his daughter and intending to nullify his daughter’s vow; if she made a nazirite vow and he thought that she had vowed to bring an offering and he annulled it with that intention; if she prohibited figs to herself and he thought it was grapes, so he annulled the vow with that intention. In all these cases, he must annul the vow again when he learns the facts, and do so for the correct woman and the correct vow. This is inferred from Numbers 30:5, “Her father did not restrain her,” meaning that he must intend the woman taking the vow; “her father heard her vow,” meaning that he knows the vow that she made. He can annul the vow the entire day that he learns the correct information.