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Nuances in the reading:
A. Not to delay more than a breath between verses:
The Megillah is to be read straight from beginning to end without interval.  One is not to delay more than one breath between each verse. [However one is to delay slightly between each chapter.]
B. The following verses are repeated out loud by the congregation:
It is accustomed for the congregation to read four verses of redemption aloud. These verses discuss the main parts of the miracle, its beginning, and conclusion. These four verses are: Ish Yehudi; Umordechai Yatza; Layehudim Haysa Ora; Ki Mordechai Hayehudi. The Chazan must [initially] repeat these verses aloud after the congregation concludes their recitation.
C. Raising the voice by Balayla Hahu:
The reader is to raise his voice when he reads the words Balayla Hahu.
D. The ten sons of Haman:
One must read the ten sons of Haman in a single breath. The custom is to read from the words חמש מאות איש until עשרת [בני המן], in one breath. [If however one is short of breath then he is to follow the Talmudic law and read from the words “Vies Parshendasa”.]
Bedieved: If one did not read the ten sons in one breath he has nevertheless fulfilled his obligation.
Congregation reading it to themselves: Some congregations have the custom to first read the ten sons to themselves and then have the Chazan repeat it. Some Poskim however have written against this custom. [The Chabad custom is like the former opinion.]
Verbalizing the words properly: The reader must beware that when he reads the words in one breath, that he verbalizes every single word of “Vies” from within the Megillah and not from memory. Furthermore each word of Vies is to be read from the word written corresponding to that son’s name, and he is not to read it from one of the former or latter words of “Vies”.
Stomping during the name of the ten sons: Some have the custom to stomp their feet on the ground while the ten sons of Haman are read. Others clap their hands on the ground. The former is the proper custom. [It is not the Chabad custom to make any noise during the reading of the ten sons, until the ending words of Aseres Bnei Haman are recited.]
Some have the custom to place their hand on their Tefillin upon reciting the word “Vikar” . [This is not the Chabad custom.]
F. Repeating Laharog and Lifneihem:
In the Megillah [8:11] we read “Laharog ule’abeid” and repeat “Vileharog ule’abeid”. In [9:2] we read “V’ish lo omad bifneihem” and then repeat “V’ish lo omad lifneihem”.
G. Shaking the Megillah:
The Megillah is rustled at the mention of the words “Ha’igeres hazos” [9:26] and again at “Igeres haPurim hazos hasheinis” [ 9:29].
H. Elongating the Vav of Vayzasa:
 M”B 690/20 based on Rama 690/5; See above Halacha 13!
 M”A 690/17; Elya Raba 690/10; M”B 690/52; Kaf Hachaim 690/90
The reason: The reason for this is because the Megillah must be read straight like a letter. [ibid]
 Aruch Hashulchan 690/21
 Rama 690/17 in name of Abudarham; Hagahos Maimanis
 Rama ibid writes “some have written that it is accustomed”. He then concludes “and so is the custom in these provinces”.
The reason: This is done in order to prevent the children from falling asleep, and help them concentrate on the reading. [M”B 689/16 in name of Levush] Alternatively it is said aloud in order to express joy. [M”B 690/58 in name of Mordechai] The Tanya rules that this is not an obligation or even a custom and is simply done to rejoice the children and have them ask why the verses were said aloud. This then instigates a conversation of the Purim miracle which spread and teaches the fear of G-d. [Mateh Moshe 1003; Kaf Hachaim 690/106]
 M”B 689/16 in name of Levush
 M”B 690/16; However Bedieved if the Chazan did not repeat the verses the congregation has nevertheless fulfilled their obligation.
 Rama 690/4; 690/17
The reason: The reason for why the Chazan is to repeat the words is because initially one is not to read the words out loud together with the Chazan and he is not to help him with the reading [Rama ibid] as one is initially required to hear each and every words from a Kosher Megillah. [M”B 690/15 and 690/58]
 Maharil brought in Darkei Moshe 690; M”A 690/17; Elya Raba 690/10; M”B 690/52; Kaf Hachaim 690/90; See Elya Raba 690/19 and Likkutei Maharich for other places that some are accustomed to raise the voice.
 The reason: The reason for this is because the main miracle occurred at this time. [ibid]
 The reason: This is done in order to publicize that all ten sons were killed and hung simultaneously. [Michaber ibid] They were first killed and then hung. [Birkeiy Yosef 690/9; Kaf Hachaim 690/92]
 Rama ibid; However from the letter of the law one must only read until Aseres [Michaber ibid] starting from the word Ish. [Beis Yosef in name of Orchos Chaim brought in Kaf Hachaim 690/89] However the M”B 690/54 writes from the letter of the law one can begin from the word Vies Parshendasa.
The reason we start from “Chamesh Meios Ish”: The reason for this is because the sons of Haman were generals over the five hundred men. [Drashos Mahril in name of Rokeiach; Mateh Moshe 1002; Darkei Moshe 690/3; Elya Raba 690/10; M”B 690/54; Kaf Hachaim 690/94]
 M”B 690/54; The Kaf Hachaim 690/95 concludes that if one will not be able to say even all ten sons in one breath then he should start from “Chameish Meios Ish” and take a breath as soon as he needs.
 Rama ibid; This applies even if one made a very long interval in-between the reading of the ten sons and then continued, nevertheless he fulfills his obligation. [P”M 690 A”A 17; Kaf Hachaim 690/93]
 Kaf Hachaim 690/91; Tzafnas Paneiach Rambam 3 Hashmatos; Piskeiy Teshuvos 690/7; Ketzos Hashulchan 3 supplements that this was the custom in Chevron
The reason: As the Chazan cannot fulfill the obligation of “one breath” for the listeners and hence they have to read it themselves. [Tzafnas Paneiach ibid] However see Piskeiy Teshuvos ibid footnote 29 that some Poskim argue on this and rule one is Yotzei also the one breath. See Taz 143/3 and Sheilas Yaavetz 1/75; Alternatively the reason is because we suspect one may miss a word due to the reader’s quick pace in trying to say it all in one breath. [Piskeiy Teshuvos ibid]
 Chayeh Adam 154/22; M”B 690/53; Kaf Hachaim 690/91
 Ben Ish Chaiy Tetzaveh 9
 Kaf Hachaim 690/97
 Ben Ish Chaiy Tetzaveh 8; Kaf Hachaim 690/96; Ketzos Hashulchan 3 supplements that the custom in Chevron was for the children to make noise while the ten sons were read by the congregation
 To note however that the Rebbe did lightly tap his feet when the ten sons of Haman were read. [Otzer Minhagei Chabad 93]
 Ben Ish Chaiy Tetzaveh 9; Kaf Hachaim 690/90; Moed Lekol Chaiy 31/88; Piskeiy Teshuvos 693/6
 As the word Vikar is expounded by the Sages to refer to the Tefillin. [ibid]
 Sefer Haminhagim p. 171 [English]; The two Nuschaos are brought in Sefer Hamesores. Shevet Hasofer 27 writes that so was the custom Chasam Sofer in his Beis Midrash and that the Chasam Sofer even wrote the extra letters in his Megillah in small. See Otzer Minhagei Chabad 98.
The custom of the Rebbe Rashab: The Rebbe Rashab was not accustomed to repeat these words and he told Rav Yaakov Landau [the Baal Korei] in 1919, prior to him reading the Megillah, that “By us it is not our custom to repeat these words”. Similarly when Rav Yaakov Landau read the Megillah for the Rebbe Rayatz he did not repeat the words Lahrog Uliabed or Lifneihem, rather he only said “Velaharog” and “Bifneihem”. [Yagdil Torah N.Y. 58 p. 138; Letter of Rav Landau to the Rebbe printed in Igros Kodesh 3/337] The Rebbe however responded that seemingly the above was Mishna Rishona [the initial custom] however later the Mishna Achrona [final stance] of the Rebbe Rayatz was to say both versions. This can be vivdly seen from the fact the Rebbe Rayatz was alive when the Chabad customs of Purim were printed and he did edit this ruling. Likewise in 1937 when I [the Rebbe] read the Megillah for the Rebbe Rayatz in this fashion he made a satisfying body response. [Igros Kodesh ibid; See Reshimos Devarim 1/187; Otzer ibid]
Other words in which there exist customs to repeat: In 1/22 the word Sorer is repeated as Shorer [Likkutei Maharich]; In 3/4 the word “Keamram” is repeated “Beamram” [See Kinyan Torah 5/86] This is not the Chabad custom.
 M”A 690/17 in name of Mateh Moshe; M”B 690/52; Elya Raba 690/10; Kaf Hachaim 690/90; They writes to shake the Megillah by Igeres Hazos; Sefer Haminhagim p. 171 [English] adds to also shake by “Igeres Hapurim Hazos”; See Igros Kodesh 12/1
The Gemara Megillah 16b states that the Vav of Vayzasa is to be elongated. There is a dispute amongst Rishonim as to the meaning of this statement. Some say that it means that when writing the letter one is to cut off the top of the Vav and make it bend downwards hence implying that all the sons were hung the same day. [Ran and Riah] Others hold it means that the Vav is to be written as a large letter [Osiyos Gedolos]. [Rosh] Others hold it means one is to stretch out the letter when reading from the Megillah. [Opinion brought in Rosh and Ran]. The Rama here records the first and last opinion as possible explanations. See Beis Yosef 691; Kol Yaakov 691/22
 Michaber ibid
 Rama ibid in name of opinion brought in Ran; Rosh; Beis Yosef; Orchos Chaim.
Other Opinions: Some rule one must elongate the writing of the Vav. [Rama ibid; See background]
 This means to say that the Vav is to be properly emphasized and not swallowed. [M”B 691/19]
 Beis Oved 691/12; Chida on Miseches Sofrim; Kol Yaakov 691/22;