Gemara

Question (Rabah): If he said 'the vow is affirmed and annulled for you at once', what is the law?

Answer: We learn from Rabah's law.

(Rabah): If two things cannot take effect one after the other (e.g. to be Mekadesh two sisters), if one tries to make them take effect at once, it does not take effect.

Rishonim

The Rif and Rosh (10:4) bring the Gemara verbatim. The Rosh concludes 'therefore, there is no Kiyum or Hafarah.'

Bach (YD 234 DH Omar): The Rosh means that we are stringent to say that there is Kiyum. Perush ha'Rosh says so explicitly.

Rebuttal (Taz 234:38): Perush ha'Rosh (DH Kayam) said that the question was whether we follow his first words, or if both of them take effect. We settle the question from one who was Mekadesh two sisters at once; neither takes effect. The same applies here, since Hafarah cannot take effect after Kiyum. This connotes that the Rosh holds that neither Kiyum nor Hafarah took effect; he can still do either of them.

Rambam (Hilchos Nedarim 13:22): If one said to his daughter or wife 'your vow is affirmed and annulled at once', it is affirmed.

Question (Ran DH u'Pashtinan): The Gemara equated this to Kidushin of two sisters. Neither takes effect at all!

Answer #1 (Kesef Mishneh and Radvaz): The Rambam explains that we learn from Rabah that since Hafarah cannot take effect after Kiyum, if one tries to do both at once, Hafarah does not take effect. According to the Ran, the Gemara should have said that neither takes effect!

Question: Why don't we say that since Kiyum cannot take effect after Hafarah, if one tries to do both at once, Kiyum does not take effect!

Answer (Kesef Mishneh): Since we can explain either way, we are stringent.

Question: The Rambam did not say that it is affirmed only due to Safek!

Answer (Kesef Mishneh): We say that it is neither affirmed nor annulled. He is quiet, and therefore it is affirmed! However, if so why doesn't the Rambam say so (that it is affirmed) regarding other Sefekos that were not resolved?

Rebuttal (Machaneh Efrayim Nedarim 38): If it is affirmed through silence, he should be able to annul until the end of the day!

Answer #2 (to Question (i) - Machaneh Efrayim): Kiyum and Hafarah can take effect one after the other, i.e. Kiyum for an hour, and then Hafarah.

Note: Perhaps he explains that the Gemara brought Rabah's law to infer that if two things can take effect one after the other, if one tries to make them take effect at once, one takes effect.

Answer #3 (Levush YD 234:40,44): The Rambam holds that any Kiyum works, even in the heart. Hafarah works only if he said it.

Note: Perhaps he means that the Kiyum and Hafarah weaken each other. A weak Kiyum helps, but a weak Hafarah does not. Alternatively, the spoken words Mevatel each other, and his intent to affirm suffices to affirm the vow.

Question (Ohr Some'ach): If one called two animals '10th', one of them becomes Ma'aser Behemah, because both can become Kodesh through a mistake (if he didn't call the 10th 'Asiri', and called the 11th 'Asiri'). Likewise, we should say that the Hafarah takes effect, because it can take effect after Kiyum, i.e. if one permitted his Kiyum! (It is as if the Kiyum was a mistake!)

Answer (and Answer #4 - Or Some'ach): The Kiyum takes effect because if we would say that neither takes effect, it is as if he said nothing. We are left with his intent. Kiyum in the heart works, but Hafarah in the heart is void.

Question (Devar Avraham 1:16 Milu'im 1:4): He intended for Kiyum through speech, not through thought! Hekdesh with an invalid expression does not work, even though thought suffices! Also, he intended for Kiyum and Hafarah together, which is invalid!

Answer #5 (Kiryat Sefer): Since both matters that he said cannot be fulfilled, the first is fulfilled.

Answer #6 (Taz YD 234:38): The Rambam holds that since he affirmed before he annulled, surely the Kiyum is not Batel (by itself). The question was whether or not the Hafarah is Mevatel the Kiyum. We answer that it is not Mevatel it, like when the Hafarah was after the Kiyum. This is unlike Kidushin of sisters. Even if he said 'Rachel and Leah are Mekudashos to me', since Mekudashos refers to both of them (we cannot put one of them before the other). We prove from sisters only that if something does not work one after the other, it does not work together.

Answer #7 (R. Chayim ha'Levi Al ha'Rambam): Kiyum of a vow prevents Hafarah from taking effect. Hafarah of a vow does not block Kiyum. Rather, after Hafarah there is no vow! The Rambam holds that the rule about two things that cannot take effect one after the other is only when one prevents the other from taking effect, but not if the case never arises. Therefore, the Hafarah does not take effect, but the Kiyum does. The Ran holds that the rule applies whenever two matters cannot take effect at the same time.

Question (Gilyon Chazon Ish): Presumably, the Torah gave him the right to choose to annul or affirm. Just like he cannot annul after affirming, he could not affirm after annulling even if the Neder were intact! If there were power to affirm after annulling, the Neder would still exist, for it can be revived through Kiyum! Also, the Gemara challenged Rabah from taking Ma'aser after Ma'aser. There also, the second Ma'aser is not inhibited due to the first, rather, because there is no more Tevel (it became Chulin)! Also, Kidushin of one sister does not inhibit Kidushin of the other, it just causes her to be Ervah, on whom Kidushin does not take effect!

Answer #8 (Pnei Yehoshua Kidushin 50b DH Ela): T he Rambam rules unlike Rabah because a Beraisa supports Shmuel (Eruvin 49b, who says that if one tried to declare Shevisah in more than four Amos, it takes effect somewhere).

Rejection (Avnei Nezer YD 304 2 and Keren Orah 69b DH Kayam u'Mufar): The Rambam rules unlike Shmuel regarding a Todah slaughtered in order to be Mekadesh 80 loaves. Tosfos (Eruvin 49b DH Mai) says that Shmuel agrees in other cases.

Ran (DH Boi): He said them at once, i.e. he said 'for you' only once (it is affirmed and annulled for you). This joins the two expressions. Alternatively, he said 'for you' twice, but he said 'at once.'

Perush ha'Rosh (DH Kayam): The question was whether or not we follow the first matter that he said.

Question (Keren Orah, ibid.): This is reasonable if he said 'for you' twice, but not if he said it only once (for then neither clause stands on its own! However, Perush ha'Rosh says that he said it only once!) In any case, if this was the question, how did we resolve it from Kidushin of two sisters?

Poskim

Shulchan Aruch (YD 234:44): If he said to her at once, 'the vow is affirmed and annulled for you', (Rema - or he said 'it is affirmed for you and annulled at once',) it is not annulled or affirmed.

Bach (ibid.): The Tur discusses saying at once 'it is affirmed for you, it is annulled for you', Toch Kedei Daibiru. It is a Safek, and we are stringent.

Rebuttal (Taz 38): This text cannot be correct. If he said 'for you' twice, and did not say 'at once', nothing joins them to be like one! '

Question: Sa'if 41 says that if one affirmed in his heart, he can annul within Toch Kedei Dibur. (Why don't we say that here also, his Hafarah works because it was Toch Kedei Dibur?)

Answer #1 (Levush): Here is different, for he said the Kiyum with his lips. It suffices for the subsequent Hafarah to Mevatel the Kiyum, but not to annul the vow, for the Kiyum is likewise Mevatel the Hafarah!

Rebuttal (Shach 62): One can always retract Toch Kedei Dibur (except for Kidushin, divorce, blasphemy and idolatry), even from speech!

Answer #2 (Shach): Here, he did not intend to retract. He wanted both of them to take effect.

Shulchan Aruch (ibid.): According to the Rambam, it is affirmed.