במדבר, פרק ל׳, פסוק ח׳

The power of silence and shared responsibility within the family unit lie at the heart of the laws governing a woman's spiritual commitments. When a woman makes a vow, the reaction of the man in her life upon learning of it seals its fate. The man is generally understood to be her husband [ביאור שטיינזלץ], though some specify that this refers to a fiancé [רבנו בחיי]. The requirement that he actually hears the vow naturally excludes a deaf husband, who is physically unable to perceive it [תורה תמימה].

If the husband stays silent on the day he discovers the vow, offering no objection, his lack of response is treated as an active confirmation [ביאור שטיינזלץ]. By allowing the day to pass without canceling the vow, it is as though he explicitly stated his desire to uphold it, a rule that equally applies to a father's silence [רש״י, מזרחי, דברי דוד, משכיל לדוד]. The window of opportunity to cancel the vow is incredibly narrow, limited strictly to the day he hears it, ending at nightfall. Even if he learns of the vow moments before sunset, he does not receive a full twenty-four hours to act; his time expires as soon as the stars appear. Once he remains silent and the vow takes effect, neither the husband nor the father can cancel it independently; the only way to undo the commitment at that point is by consulting a sage [בכור שור]. However, a husband or father does possess the authority to issue a general, sweeping cancellation of future vows before even hearing them, provided the woman is still under their jurisdiction [רש״ר הירש].

An unusual phrasing regarding the timing of this silence sparks a deep legal debate. According to Maimonides, the specified day of hearing actually refers to the father's hearing. In this view, a fiancé can only cancel the vow if he learns of it on the exact same day the father does, because the father's cancellation is entirely invalid without the fiancé's joint participation [רבנו בחיי, צפנת פענח, העמק דבר, הכתב והקבלה, ברכת אשר]. Conversely, other scholars maintain that the fiancé's timeline is completely independent of the father's. To explain the unusual phrasing, they suggest that hearing implies more than just perceiving a sound; it denotes active acceptance and agreement. Therefore, the vow is upheld in one of two ways: either the husband actively shows his agreement on the day he hears it, or he simply remains silent. This perspective relies on the understanding that when a husband hears a vow and intends to uphold it, he deliberately chooses silence as his method of approval [העמק דבר, הכתב והקבלה].