Nedarim, Chapter Eleven, Mishnah Four
The first part of the mishnah discusses a woman who vows not to provide benefit for either her own or her husbands father or brother. The second part discusses a woman who vows not to provide benefit for her husband himself.
1) [If she vows,] Konam that which I do for my father, [or] your father, [or] my brother, [or] your brother, [the husband] cannot annul it.
2) [Konam] that which I do for you, he need not annul it.
a) Rabbi Akiva says: he should annul it, lest she make more than is fitting for him.
b) Rabbi Yohanan ben Nuri said: he should annul it, lest he divorce her and she thereby be forbidden to him.
Section one: In all of these cases the woman vows that anything that she produces shall be forbidden to either her or her husbands father or brother. Since none of these vows involves self-denial, the husband may not annul the vow.
Section two: We learned in the fifth chapter of Ketubot that a woman is obligated to perform certain duties for her husband and her handiwork belongs to him. Since she has this obligation, she may not vow that her husband may not benefit from her handiwork. In essence, she does not own her handiwork and therefore it is not hers to prohibit by vow.
Rabbi Akiva points out that not all of the handiwork automatically goes to her husband. According to Ketubot 5:9, she has a set amount of handiwork which she must do; anything over that amount she gets to keep. If so, the vow is potentially effective for this extra amount. Since if she does produce an extra amount, it will be difficult for a husband not to derive some benefit from it, he should annul the vow to avoid the potential problem. The reason that he has a right to annul the vow even though it is not a vow of self-denial is that this is something that comes between him and her.
Rabbi Yohanan ben Nuri points out that if the husband divorces his wife, the vow will become valid, since she is no longer obligated to provide him with her handiwork. Once divorced, he will also no longer be able to annul the vow. In such a case he would not be able to remarry her. To avoid this problem, Rabbi Yohanan ben Nuri suggests that the husband annul the vow.