Gemara

(Mishnah): A husband cannot annul the Nezirus of his wife after Zerikah (throwing the blood on the Mizbe'ach) of one of her Korbanos;

R. Akiva says, he cannot annul after Shechitah (slaughter) of a Korban;

This applies to (Korbanos brought for) Tiglachas (shaving after finishing Nezirus in) Taharah. If this was Tiglachas Tum'ah, he can annul. He can say that he does not want a wife who is Menuveles (repulsive, due to Nezirus).

R. Meir says, even if it was Tiglachas Taharah, he can annul, for he can say that he does not want her to shave her hair.

Our Mishnah is unlike R. Eliezer. He forbids wine (and Tum'ah) to a Nazir until he shaves. Since Nivul remains, he would be able to annul. Our Tana permits wine right after Zerikah, therefore there are no grounds to annul. R. Akiva does not allow Hafarah after Shechitah, for this would invalidate the Korban.

Question (R. Zeira): We could do Zerikah Lo Lishmah (intend for a Nedavah, i.e. a voluntary offering), and the meat would be permitted!

(Beraisa): If Shechitah of the lambs (Shelamim that accompany Shtei ha'Lechem) of Shavu'os was Lo Lishmah, we may do Zerikah (unless it is Shabbos), and the meat may be eaten.

Answer: Indeed, after Shechitah of the Olah or Shelamim, (he may annul, and) we may do Zerikah (l'Shem Nedavah), and the Korban is not lost!

The case is, the Chatas was slaughtered first. (It is invalid Lo Lishmah).

(Mishnah): This applies to Tiglachas Taharah. If it was Tiglachas Tum'ah, he can annul, for he can say that he does not want a repulsive wife;

R. Meir says, even if it was Tiglachas Taharah, he can annul it, for he can say that he does not want her to shave her hair.

The first Tana does not allow Hafarah for this, for she can wear a wig! R. Meir holds that a man would be repulsed if his wife wore someone else's hair.

Rishonim

Rambam (Hilchos Nezirus 4:17): If a Nezirah brought Korbanos Tiglachas Taharah and Zerikah was done for one of them and then her husband heard her vow, even though she did not shave yet, he cannot annul it. If he heard before Zerikah, he can annul it. Regarding Tiglachas Tum'ah, he can annul even if she offered Korbanos Nazir Tamei, for otherwise she must be a Nezirah again.

Radvaz: The Halachah follows the first Tana, who says that he cannot annul if it was Tiglachas Taharah, for she can wear a wig. If it was Tiglachas Tum'ah he can annul, lest she become repulsive through repeating Nezirus.

Rambam (Hilchos Nedarim 12:4-5): A husband can annul a vow of Inuy (affliction) even if it is for a short time, e.g. not to drink wine today.

Perush ha'Rosh (28a DH Masnisin): After Zerikah she may drink wine and become Teme'ah, therefore it is no longer Inuy Nefesh.

Tosfos (DH Nizrak): Even if Zerikah will be done very soon and she will be permitted to drink, this is Inuy Nefesh and he can annul.

Sefas Emes (28a DH uv'Emes): Because she has been deprived of wine for so long, even a tiny addition to this is considered Inuy. Why did the Gemara say that R. Akiva forbids only after Shechitah of the Chatas, lest the Korban be lost? Perhaps he does not consider a tiny addition to be Inuy!

Question: Why does the Mishnah say that he can say 'I do not want her to be Menuveles (through another Nezirus)'? He can annul it due to Inuy Nefesh!

Answer (Tosfos DH ba'Meh): Sometimes 'Menuveles' refers to Inuy. The Mishnah said 'I do not want...' due to R. Akiva. For a small Inuy (until all the Korbanos are offered), he does not allow Hafarah that disqualifies Korbanos. He allows it to avoid major Inuy of another Nezirus. Alternatively, 'I do not want...' is for parallel structure with R. Meir, allows Hafarah if he does not want her to shave her hair.'

Keren Orah (DH ba'Meh): What is the Chidush that R. Akiva permits Hafarah after offering Korbanos Nazir Tamei? She offers them even if he annuls, for we hold that Hafarah is not retroactive! (It is a Chidush according to the opinion that Hafarah uproots retroactively.) We discuss when the animal was hers. If it was his, retroactively it was Chulin! If we are concerned for Chulin b'Azarah, then Olah and Shelamim are just like Chatas!

Perush ha'Rosh (DH v'Rebbi): R. Akiva agrees that if he annulled, it is annulled. However, the Gemara connotes that it is not annulled, just like the first Tana holds that he cannot annul even b'Di'eved. However, it would be astounding to say that she would bring a Korban for Tum'ah after he annuls.

Tosfos (DH Rebbi): According to R. Akiva, if he annulled, it is not clear whether it works, or if not, for Chachamim can uproot the Torah by telling one to be passive.

Tzafnas Pa'ane'ach (2:33:2): Chachamim forbid her even if he annuls, so his Hafarah does not lighten her Inuy, so mid'Oraisa he cannot annul.

Sefas Emes (28a DH b'Mishnah): If R. Akiva holds that the Hafarah does not work b'Di'eved, perhaps the first Tana agrees that l'Chatchilah one may not annul after Shechitas ha'Chatas, lest it be lost! The Rambam connotes that one may annul after Shechitah of any Korban.

Poskim

Shulchan Aruch (YD 234:59): If a woman vowed to forbid pleasure of bathing or adorning, even if she forbade only if she will bathe or adorn today, this is Inuy Nefesh.

Beis Yakov (152): It seems that a vow for less than a day is not Inuy. However, we learn from Nazir that he can annul it.

Rebuttal (Mishneh l'Melech Hilchos Nedarim 12:4): The Shulchan Aruch cites the Rambam, who forbids even a short time. 'Today' forbids until dark. This is Inuy even if she vowed shortly before dark! The proof from Nazir is invalid, for there it was part of a long vow.

R. Akiva Eiger (15): The Rosh (Nedarim 80a DH Ela (2)) says that Inuy for one day is not called Inuy, but if she forbade food if she will bathe today he can annul. Nivul for a day is Nivul, so she is apt to bathe today.