Holding authority over another person's spiritual commitments carries a heavy burden of responsibility. In a relationship where one individual has the power to validate or cancel the vows of another, misusing that authority does not erase the action. Instead, it shifts the blame from the person who commits the act to the one who caused the failure.
The exact moment a husband attempts to break his wife's vow is a matter of discussion. One perspective suggests a situation where the husband remains silent, waits until the following day, and only then attempts to cancel the commitment [ספורנו, שד״ל, רלב״ג, בכור שור]. However, the primary approach among commentators is that his initial reaction goes beyond merely listening to the words; it implies immediate acceptance and agreement. In this scenario, the husband hears the vow, explicitly agrees to uphold it, but later regrets his decision and tries to cancel it, even on that very same day. Because he already gave his approval, any subsequent attempt to cancel the vow is entirely invalid. Even if he initially possessed the right to nullify the commitment, that power is no longer in his hands [אור החיים].
This dynamic introduces a fundamental rule: a person who causes another to stumble steps into their place and bears their punishment. Most commentators explain this through a scenario where the husband tells his wife he has canceled her vow, and she trusts his word. Because she acts unintentionally, completely unaware that the cancellation was legally invalid, she is entirely free from punishment. The husband bears the full guilt for the broken vow because he misled her. Another perspective on this transfer of guilt focuses on the relationship of authority. Since the wife is under his authority, he might simply force her to violate the vow [אבן עזרא, ספורנו, רלב״ג]. There is, however, an important distinction. If the husband merely tries to persuade her to break the vow and she willingly agrees to listen to him, the guilt falls on her own head. He only bears her guilt when he explicitly forces her or misleads her into thinking the action is permitted [העמק דבר].
A different situation arises if the wife is well versed in the law and knows perfectly well that her husband did not cancel the vow in time. In such a case, where she acts with full intent and awareness, she is held responsible and faces punishment. Yet, the husband does not escape consequence. His punishment here is not for misleading her, but stems from the fact that he had the ability to protest and stop her from sinning, yet chose to remain silent [רמב״ן, הטור הארוך].
On a deeper level regarding the laws of vows, the reason the husband bears the guilt goes beyond simply causing his wife to stumble. When a husband upholds his wife's vow, the Torah treats the situation exactly as if he had made the vow himself. Therefore, when he later causes her to violate it, he is personally transgressing the prohibition against breaking his own word, making the guilt directly his own [חתם סופר].