Nazir 21b:
הריני נזירה ושמע בעלה ואמר ואני אינו יכול להפר: איבעיא להו בעל מיעקר עקר או דלמא מיגז גייז למאי נפקא מינה
§ The mishna taught that if a woman said: I am hereby a nazirite, and her husband heard and said: And I, he cannot nullify her vow. A dilemma was raised before the Sages: When a husband nullifies the vow of his wife, does he uproot his wife’s vow, making it as though she never vowed, or perhaps he merely severs her vow from that point onward, but her vow was still in effect until he nullified it? The Gemara asks: What difference is there resulting from this dilemma?
לאשה שנדרה בנזיר ושמעה חברתה ואמרה ואני ושמע בעלה של ראשונה והפר לה אי אמרת מיעקר עקר ההיא נמי אישתראי ואי אמרת מיגז גייז איהי אישתראי חברתה אסירא מאי
The Gemara explains that the difference is with regard to a woman who vowed to be a nazirite, and another woman heard and said: And I, and the husband of the first woman heard and nullified her vow. If you say that the husband uproots the vow entirely, the vow of that second woman should also be dissolved, as she associated herself with a non-existent vow. And if you sayhe severs it from this point, the vow of his wife is dissolved, but the other woman remains bound by her vow, as the first vow was intact when she associated herself with it. What, then, is the answer to this dilemma?
ת"ש הריני נזירה ושמע בעלה ואמר ואני אינו יכול להפר ואי ס"ד בעל מיגז גייז ליפר לאשתו והוא ליתסר אלא לאו ש"מ בעל מיעקר עקר
The Gemara suggests: Come and hear the statement of the mishna: If she said: I am hereby a nazirite, and her husband heard and said: And I, he cannot nullify her vow. And if it should enter your mind that the husband severs the vow from that moment onward, let him nullify the vow for his wife and he will remain bound by his vow, since if the vow is not nullified retroactively, her vow was intact when he associated himself with it. Rather, must one not conclude from the mishna that the husband uproots the vow entirely, which means he would also uproot his own vow by nullifying hers, and that is why he is unable do so?
לא לעולם מיגז גייז ובדין הוא דליפר לה והיינו טעמא דלא מצי מיפר כיון דאמר לה ואני כמאן דאמר קיים ליכי דמי אי מתשיל אהקמתו מצי מיפר ואי לא לא מצי מיפר
The Gemara refutes this argument: No; actually, one can say that the husband severs the vow from that point onward. And if there were no other points to consider, by right the mishna should have taught that he can nullify her vow for her; and this is the reason why he cannot nullify it: Since he said to her: And I, he is considered like one who said: It is upheld for you, and once a husband has upheld his wife’s vow he can no longer nullify it. Consequently, if he requested to have his upholding dissolved by a Sage, he can nullify her vow, and if not, he cannot nullify it. Consequently, the ruling of the mishna does not resolve the dilemma.
Why does the Gemara have to add that he can perform שאלה on his הקמה and then be מיפר for he. That is seemingly pashut?! All the Gemara had to tell us was that the reason he can't nullify her vow is because he did הקמה! The rest we can figure out on our ownnnnnn!
