Today’s daily Halacha is dedicated in the memory of Simcha Freida Bas Tzemach, whose Yartzite is today.
What is the law if one recited Zachreinu or Mi Chamocha in Shemoneh Esrei after Aseres Yimei Teshuvah?
One who recited Zachreinu or another of the fours stanzas during Shemoneh Esrei when it is not Asaeres Yimei Teshuvah, is to repeat the Shemoneh Esrei as a Toras Nedava. If he remembered in the midst of the stanza then he is to immediately stop reciting it. If he remembers after completing the blessing then he is to continue with Shemoneh Esrei and after its conclusion repeat Shemoneh Esrei as a Toras Nedava.
Sparks of Kabala
Mi Chamocha & Gilgul Neshamos:
On the day of Rosh Hashanah all the souls which require reincarnation into this world [i.e. Gilgul] are judged. This is why the dialect Mi Chamocha, which is added during Aseres Yimei Teshuvah, contains the words “Zocher Leyitzurav Berachamim Lechaim” [remember your creations with mercy for life] and not “Zocher Osanu” or “Zachreinu” [remember us] as is said by the other added stanzas. The reason is because it includes a request of mercy for the souls that will be returned to bodies in this world. It is also for this reason that this stanza was added in the blessing of Techiyas Hameisim [Mechayeh Meisim-resurrection], as it hints to the future life of the souls requiring a Gilgul.
At the conclusion of Shemoneh Esrei, after Elokaiy Netzor, one says “Oseh Hashalom” in place of “Oseh Shalom”. [This is likewise stated in Kaddish-see Halacha 4. However in Birchas Hamazon the Nussach is Oseh Shalom and not Hashalom. Likewise in the last blessing of Shemoneh Esrei, Sim Shalom, the dialect is not changed.]
Oseh Hashalom: At the conclusion of Kaddish one says “Oseh Hashalom” in place of “Oseh Shalom”.
Ulieila: It is not the Chabad custom to add the word “Ulieila” in Kaddish of Aseres Yimei Teshuvah [with exception to the Kaddish said during Neilah in which we say Lieila Ulieila Mikol Birchasa].
 Ketzos Hashulchan 21/4; Admur 108/18 regarding Yaleh Veyavo
Admur ibid records a dispute regarding the law in this case: Some opinions [Michaber 108/12; Orchos Chaim] rule that the mention of the days of other events in Shemoneh Esrei does not invalidate the prayer or that blessing to require the repetition of Shemoneh Esrei or of that blessing. Others [Olas Tamid 108/18; Taz 108/12] however rule that it has the same law as one who spoke in the midst of Shemoneh Esrei, in which the law is that he must repeat that blessing or return to the beginning of Davening, as explained in 114/4. Practically Admur concludes: (Regarding the final Halachic ruling) although we apply the rule of Safek Brachos Lihakel, nevertheless since even if one were to pray the entire day it would be praiseworthy, therefore whenever there is a case of doubt one should simply repeat the prayer as a Toras Nedava, and it is not necessary to novelize anything in his Nedava prayer. [Admur ibid]
Other Poskim: Some Poskim rule one is required to repeat Shemoneh Esrei. [Derech Hachaim brought in Ketzos Hashulchan ibid]
 Shaar Hakavanos p. 97; Kaf Hachaim 582/34
 Siddur Admur [omitted in Shulchan Aruch]; Shaar Hakavanos 190; Peri Eitz Chaim Shaar R”H 7; Kaf Hachaim 582/15; M”E 582/1 and 22
The reason: The Gematria of Hashalom is the same as Safriel Hamalach which is the angel which writes the Jews in the book of life during Aseres Yimei Teshuvah. [Peri Eitz Chaim ibid brought in Kaf Hachaim ibid; M”E ibid] In however Hagahos Mordechai [Miseches Rosh Hashanah 720 he states as follows: Safiriel is the Gematria of Oseh and Oseh is the Gematria of Hashalom. Alternatively this hints to the kindness of Hashem that swerves the judgment to merit in a case that the sins and merits are equal, and the verse states “Maaseh Hatzedaka Shalom”.
 Hisvadyos 1984 1/28 [The Rebbe stated that he asked this question to the Rebbe Rayatz, and after a discussion on the matter the Rebbe Rayatz replied that one is not to swerve from the dialect written in the Siddur.] See also Kuntrus Hasiddur [Hakdama] that this question is raised.
 Siddur Admur does not change the Nussach of Sim Shalom during Aseres Yimei Teshuvah or Rosh Hashanah. This follows the custom of the Sefaradim brought in Shalah [Tefilas Rosh Hashanah] that one may not change the dialect. The Shaar Hakolel 9/35 states that those that change the dialect of the concluding blessing of Sim Shalom to “Oseh Hashalom” [see custom of Ashkenazim] are changing from the dialect of the Sages and transgress the prohibition of “Lo Sisa” [not to say Hashem’s name in vain]. Likewise the concluding blessings in Shemoneh Esrei all contain 113 letters corresponding to the 113 words in the prayer of Chana, and they thus swerve from this institution by changing the concluding blessing.
Ashkenazi custom: The widespread custom of Ashkenazi Jewry from the times of the Rishonim is to conclude the blessing of Sim Shalom with “Besefer Chaim….Baruch Ata Hashem Oseh Hashalom” instead of “Hamevareich Es Amo Yisrael Bashalom”. This is followed through Aseres Yimei Teshuvah. [Artscroll Siddur]
 Siddur Admur; M”E 582/1 and 22; Piskeiy Teshuvos 582/9; not found in earlier sources.
The reason: See Halacha 5D and footnotes there. To note however that this change of dialect in Kaddish is not found in previous sources and thus is disputed against, as explained next.
Other opinions: Some write that according to the Kabalists one is not to change the dialect in Kaddish and is rather to always say Oseh Shalom as is said during the year. The change is only made by the end of Shemoneh Esrei. [Kaf Hachaim 56/38; Alef Hamagen 582/37]
Custom of Sefaradim: The Sefaradim are accustomed to only recite Oseh Hashalom in Kaddish Tiskabel that follows Shemoneh Esrei. They do not recite it by other Kaddeishim. [Moed Lekol Chaiy 13/69; Piskeiy Teshuvos 582/9; See Yalkut Yosef Moadim p. 26 ]
 Siddur Admur [no difference of Nussach is mentioned]; Gloss of Tzemach Tzedek [printed in Shaar Hakolel 4/9]; Piskeiy Hassidur 171; Sefer Haminhagim p. 118 [English]; Kaf Hachaim 582/39 based on Arizal [regarding all Aseres Yimei Teshuvah, however including Neilah] and so is the custom of the Sefaradim [Piskeiy Hassidur ibid]; Shaar Hakolel 4/9 based on Seder Hayom that explicitly says to not say it and Mishnes Chassidim and Siddur Yaakov Kopel that omits it.
The reason: The dialect of Kaddish contains exactly 28 words according to Kabala. Based on this one is not to change the dialect even during Aseres Yimei Teshuvah. [Kaf Hachaim ibid] However the M”E 582/1 writes that when Lieila is repeated the word Min Kol Birchasa is omitted and read as Mikol Birchasa, and hence there remain only 28 words.
Ruling of Admur in Shulchan Aruch: In Shulchan Aruch of Admur 582/16 he rules that one adds “Lieila Lieila” throughout all the Kaddeishim recited during Aseres Yimei Teshuvah.
Other Poskim: The following Poskim write one is to recite Leila Ulieila throughout Aseres Yimei Teshuvah: Levush 582/8; M”A 584/4; Admur ibid; M”B 582/16; M”E 581/1; Siddur Yaavetz; Kitzur SHU”A 129/1; Darkei Chaim Veshalom 706; Luach Eretz Yisrael. All the above Poskim write that one is to repeat “Lieila Lieila”. However in some Sefarim it says “Lieila Ulieila”. [Likkutei Mahrich; Piskeiy Teshuvos 582/9] The reason for repeating the word Leila is because during Aseres Yimei Teshuvah Hashem sits in judgment and His name is hence glorified before the masses much more than the regular year. Hence they emphasize that He is very exalted during this time. [Machatzis Hashekel 582/4 in name of Levush ibid] Some Poskim rule it is only to be repeated on Rosh Hashanah and Yom Kippur. [Elya Raba 582]
 Sefer Haminhagim p. 125 [English]; Hayom Yom 10th Tishrei; Kuntrus Hashulchan p. 63 based on Mamar of Rebbe Maharash [Toras Shmuel 1874 p. 284]; See Otzer Minhagei Chabad 262
Other opinions: The Shaar Hakolel 4/9 states that it is not to be repeated at all even during Neilah and that doing so has no source.