Gemara

(Mishnah): If a woman said 'I will be a Nezirah after 30 days' (and her husband annulled it, it is annulled), even if she was widowed or divorced in the 30 days.

(Beraisa - R. Yishmael): If a woman vowed 'I will be a Nezirah when I get divorced' and she was divorced, her husband cannot annul the vow;

R. Akiva says, he can.

(Rav Chisda): Our Mishnah is like R. Akiva.

Objection (Abaye): Our Mishnah can even be like R. Yishmael.

In the Mishnah, the vow is contingent on days. Since the days could expire before she gets married or divorced, R. Yishmael agrees that her status (married or single) at the time determines whether or not it may be annulled. In the Beraisa, the vow is contingent on marriage.

89b (Beraisa - R. Noson): If she said 'I may not benefit from my or your father if I benefit you', he cannot annul this;

Chachamim say, he can annul.

A man forbade himself to benefit from the world if he marries before learning. He tried to learn, but was unable to. Rav Acha bar Rav Huna tricked him into marrying, then brought him to Rav Chisda to permit his vow.

Rava: Rav Acha is brilliant! He holds that Chachamim and R. Noson also argue about Heter of a Chacham, like they argue about Hafarah. (Therefore, he had to make the vow be Chal before it could be permitted.)

(Rav Papi): They argue only about annulment.

All agree that a Chacham cannot permit a vow before it takes effect - "he will not profane his word (he will do like he said." This is after it took effect, and he will not profane his word, but others may.)

(Ravina citing Rav Papi): They argue only about Hafarah, but all agree that a Chacham can permit a vow before it takes effect - "he will not profane his word." (Others may profane his mere word, i.e. even it did not yet take effect.)

Ravina would deny that the episode (in which Rav Acha bar Rav Huna tricked a man who vowed) ever happened.

Question (Beraisa #1): If one said 'I may not to benefit from Ploni; also, from a Chacham who will permit that vow', a Chacham may permit the first vow, and then the second.

If a Chacham could permit a vow before it takes effect, he could permit either vow first!

Answer: 'The first vow' refers to the first he permits, but it may be either vow!

Question (Beraisa #2): If one said 'I will not benefit from Ploni; I am a Nazir when a Chacham will permit my vow', a Chacham may permit the vow, and then the Nezirus.

According to Ravina, he could permit either vow first!

Ravina is refuted.

Pesachim 4b (Abaye) Question: It says "Shiv'as Yomim Se'or Lo Yimatzei b'Vateichem", and it says "Ach ba'Yom ha'Rishon Tashbisu Se'or mi'Bateichem!"

Rishonim

Rif: Rava praised Rav Acha. He holds that Chachamim and R. Noson argue not only about Hafarah, but also about Heter Chacham. Rav Papi holds that they argue only about Hafarah, but no one allows Heter Chacham until it is Chal.

Rambam (Hilchos Shevu'os 6:14): If one swore not to speak with Ploni, and later swore that if he permits the first oath he will never drink wine, he can ask a Chacham to permit the first oath, and afterwards he can ask to permit the second. One cannot permit an oath or vow until it is Chal. Therefore, if in Nisan one vowed not to eat meat for 30 days starting Rosh Chodesh Iyar, and regretted it, he cannot ask to permit it until Iyar enters.

Rosh (11:6): Rava praised Rav Acha for enabling Hatarah according to R. Noson. This does not show that the Halachah follows R. Noson. He praised him for fulfilling all opinions. Rabanan (after the Gemara) rule like Rav Papa, that they argue only about Hafarah!

Ran (90a DH Mihu): If the Tanai is something that she is prone to transgress, it is as if she already did so, so it may be permitted immediately.

Ran (Teshuvas 51, cited in Beis Yosef DH Kosav ha'Ran): If one vowed not to be in a certain city next Shabbos, and just before Shabbos he regretted it, it is as if it was Chal. A Chacham can permit it. R. Noson and Chachamim argued about (Hafarah of) vows dependent on an action, e.g. '... if I will work for father' or 'I may not benefit from a Chacham who will permit my vow.' A vow contingent on time is Chal immediately, just it is Mechusar Zeman (postponed). The Rambam does not allow permitting such a vow until the time comes; I disagree. If such a vow could not be permitted immediately, a Tana would have taught this Chidush! The Rambam could agree about an oath not to be in a city, since it requires leaving the city before Shabbos. This hinges on how we explain Abaye's question in Pesachim. (Rashi explains that the two verses contradict each other. Since we cannot possess Chametz for any part of Pesach, the Mitzvah to destroy must be before Pesach!) Here, Rashi would say that the oath takes effect before Shabbos begins. Others (Tosfos) say that Abaye asked what we learn from the extra verse. (There was no difficulty, for the Mitzvah to destroy and the Isur Chametz come simultaneously.) They would say that the oath is not Chal until Shabbos. Then, he must leave. This is an even argument. Surely, he should leave beforehand, for we are stringent about a Safek mid'Oraisa. However, a Chacham may not permit it, for perhaps the Halachah follows Tosfos. If Safek mid'Oraisa l'Chumra (we must be stringent) is mid'Oraisa, the oath was already Chal due to the Safek. The Rambam holds that Safek mid'Oraisa l'Chumra is mid'Rabanan, but Chulin 11a connotes otherwise. Also, even according to the Rambam, the oath was already Chal according to Rashi. And even if the oath was not Chal yet, the primary opinion allows a Chacham to permit it because it depends on time.

Poskim

Shulchan Aruch (YD 228:17): One cannot permit a vow until it is Chal.

Shach (30): If a Chacham permitted, b'Di'eved it is not permitted.

Shulchan Aruch (ibid.): Therefore, if one vowed not to eat meat for 30 days starting Rosh Chodesh Iyar, he cannot ask to permit it until Iyar enters.

Beis Yosef (DH v'R. Yerucham): The Rambam, Ra'avad, Rashba and R. Yonah hold that even a vow dependent on time may not be annulled until it is Chal. We follow them, even though others hold like the Ran.

Rashba (Teshuvah attributed to Ramban 271): Rav Chisda does not distinguish between a vow dependent on time or on an act. R. Akiva and R. Yishmael argue about whether it may be annulled immediately, or only after it is Chal. Abaye explained otherwise, but perhaps this is a mere Dichuy and he really agrees. One should be stringent, especially since it is mid'Oraisa.

Taz (22): Perhaps the Rambam explains like this, and rules like Rav Chisda.

Shulchan Aruch (ibid.): Even if we are concerned lest the Noder transgress, we do not permit it until it is Chal.

Source (Teshuvas Ran 51, cited in Beis Yosef DH v'Chosav ha'Ran): The Torah does not authorize a Chacham to permit before it is Chal. Who allows because there is concern for transgression, and says that it is permitted?!

Rema: All the more so, if one vowed on Tanai (conditionally), we do not permit it until it is Chal.

Shulchan Aruch (229:9): If one swore not to benefit from Ploni; also, from a Chacham who will permit that vow', a Chacham may permit the first vow, and then the second. The same applies if he swore not to benefit from Ploni, and accepted Nezirus if he will permit this.