[1] 295/1

[2] This prayer consists of the last verse of Psalm 90, the entire psalm 91 “Yosheiv Beseiser”, and the Seder of Kedusha found in the prayer of Uva Letziyon. Nevertheless we do not begin reciting from Uva Letziyon but rather from Veata Kadosh. The reason for this is because the Geula cannot arrive during the night, therefore we omit this verse of Uva Letziyon which mentions Moshiach coming. [ibid] We also do not say the verse of Vaani Zos Berisi as this verse is only said together with the previous verse of Uva Letziyon. [Taz 295/1]

Repeating Orech Yamim: We repeat the verse of “Orech Yamim Asbieihu” in order to complete the name of G-d which derives from this verse. [Admur ibid] This is calculated as follows: Hashem’s name Yud Kei Vav Kei when written in full [Miluiy] is the Gematria of 130, which is the number of letters in the verse when it is repeated. Likewise when the verse is repeated there are a total of 130 words in the Mizmor. [Magen Avraham 293/1; Machatzis Hashekel there] The Tashbatz explains this to mean that there are 130 letters in total when the verse is repeated, and this is the numerical value of Hakohanim, as the Kohanim of the Hashmonaim would say this verse 7 times and win the war. [M”A ibid; Kaf Hachaim 295/1]

[3] The general reason for saying these prayers is to lengthen the stay of the Reshaim outside of Gehenim, as they do not return to Gehenim after Shabbos until the last community finishes the end of Vayehi Noam. In particular the prayer of Vayehi Noam is said because it is a prayer of blessing which Moshe blessed the Jewish people after the Mishkan was completed. [ibid; See Piskeiy Teshuvos 195/1 for a full analysis on this subject]

The reason for why we specifically mention the Seder Kedusha is because it has the ability to cool off the flames of Gihenim which are relit after Shabbos. [Mateh Moshe in name of Rokeiach brought in Shaar Hakolel 31/1]

Other reasons:

• On Motzei Shabbos the forces of evil are aroused and swerve around the world/ We therefore recite the verses of Yosheiv Biseiser as a protection against these spirits. For this reason we do not say it when Yom Tov falls during that week as the Yom Tov itself protects one from these forces and there is thus no need for an extra prayer. [Yavetz brought in Taamei Haminhagim 402]
• The paragraph of Yosheiv Biseiser with Vayehi Noam includes 248 words when repeated twice which corresponds to the 248 limbs By repeating the last versus twice it is considered as if we have repeated the entire prayer. This helps protect the limbs for the coming week. [Abudarham brought in Taamei Haminhagim 405]

^[4] 295/3

[5] This includes also the prayer of Ata Kadosh. The reason it is accustomed to omit also Ata Kadosh is because the prayer of Ata Kadosh is said as a result of saying the prayer of Vayehi Noam. As once the Shechina resides below, as is stated in the prayer of Vayehi Noam which discusses the Mishkan, it is then fit to sanctify it with the prayer of Ata Kadosh. Thus since Vayehi Noam is omitted, [for the reason to be explained in the next footnote] so too we omit Ata Kadosh. [ibid]

Other Opinions: The above follows the Ashkenazi custom, as brought by the Tur. However the Sefardi custom is to only omit Vayehi Noam and Yosheiv Neseiser and they begin from Orech Yamim, and then say Ata Kadosh. [Tur] Some however say the Sefaradi custom is to recite it entirely, as rule the Sefaradi sources brought in the next footnote. [Piskeiy Teshuvos 294/2]

[6] The reason for omitting Vayehi Noam is because within the prayer we say twice “And the work of our hands”, hence all the days of the coming week have to be fit for work. If not then we simply omit the prayer. [ibid; See Piskeiy Teshuvos 294/2 for a thorough analyses on this subject]

Other Opinions: Some, based on Kabala of Arizal, always recite the prayer of Vayehi Noam on Motzei Shabbos, even when a Holiday falls that week, and even on Motzei Shabbos Chol Hamoed. Nevertheless in such circumstances they recite it quietly. Their reasoning is because Vayehi Noam affects the influence of Shabbos on the weekday which is needed every week, without exception. [Bircheiy Yosef brought in Shaareiy Teshuvah 295/2; Kaf Hachaim 295/9-10]

[7] So rules Admur ibid

Other Opinions: Some rule that even in such a case that Yom Tov falls on Shabbos, Vayehi Noam is omitted the Motzei Shabbos prior to it. [See Kaf Hachaim 295/6]

[8] Kaf Hachaim 295/7

[9] Shaareiy Teshuvah 295/2; Kaf Hachaim 295/8

As these days are not days of a prohibition in doing Melacha.

[10] 559/2

[11] 295/2

[12] For reasons known to them. [ibid] The reason is based on Kabala, to draw down from Oar Chozer of Bina. [see Kaf Hachaim 295/1; Peri Eitz Chaim Shaar Shabbos 24]

[13] Piskeiy Teshuvos 295/1

[14] This is a widespread Chabad custom in various Shuls. It however is not all inclusive. See next footnote.

[15] However the Rebbe’s custom when he was Chazan, as heard on audios of the Rebbe’s Davening, was to recite it out loud during the week by Shacharis, and so is implied from 59/2.

^[16] So is implied from Admur 295/3, and so rules: Peri Megadim 295 M”Z 2; Poskim brought in Sharreiy Teshuvah 295/2; M”B 295/3;

The Chabad Custom: Rav Yaakov Landau writes in his diary that the Rebbe Rashab would recite Vayehi Noam in such a case, and so is recorded to be the custom of the Rebbe. [Kitzur Halachos 293 footnote 9] However in the Luach Kolel Chabad they write that it should not be said. See Nitei Gavriel Pesach 1, and Otzer Minhagei Chabad Nissan.

[17] Sheialas Yaavetz 19 brought in Shaareiy Teshuvah 295/2; Kaf Hachaim 295/7; Minchas Shabbos 96/7; Luach Tuchinskiy writes that so is the custom in Eretz Yisrael; They say that it should not be said when Pesach falls on Shabbos, as Erev Pesach is considered a holiday, being that its forbidden to do work from Chatzos. 

[18] Mishneh Halachos 6/16; See Piskeiy Teshuvos 295/2

[19] Kaf Hachaim 295/3 in name of Kneses Hagedola

Vetzaruch Iyun as the source of the Kaf Hachaim is from the Kneses Hagedola, which is the same source as the M”A and they both say different customs. After researching within the text of the Kneses Hagedola [295] the following was discovered: The Kneses Hagedola first records a custom of a community to omit both Vayehi Noam and Yosheiv Beseisar in the house of a mourner, and they would begin from Orech Yamim. He then concludes that he accustomed his community to omit only Vayehi Noam and not Yosheiv Beseiser. Hence both customs are written in the Kneses Hagedola.

[20] Kneses Hagedola brought in M”A 495/1 [This was the personal opinion of the Kneses Hagedola, as explained in previous footnote]

[21] The reason for skipping Vayehi Noam is because it mentions work, and a mourner is forbidden in work.

[22] Ketzos Hashulchan 93 footnote 15

[23] From the fact that Admur omitted this ruling of the M”A in name of the Kneses Hagedola. [ibid]

[24] Piskeiy Teshuvos 295/3

[25] See Piskeiy Teshuvos 295 footnote 26

[26] As although an Avel is forbidden in Melacha nevertheless it is permitted for others and hence is not to be omitted. [Piskeiy Teshuvos ibid]

[27] Lehoros Nasan 13/119 Brought in Piskeiy Teshuvos 295/3

[28] Kaf Hachaim 295/5