Shabbos Mevarchim Tishrei:
Tehillim: The entire book of Tehillim is recited before Shacharis just as on any other Shabbos Mevarchim.
Farbrengen: At the conclusion of the prayers one is to have a Chassidic gathering as is done on every Shabbos Mevarchim. This gathering is to include good and practical resolutions in matters of spiritual and physical charity.
Omitting Vayehi Noam: The entire prayer of Vayehi Noam is customarily omitted on the Motzei Shabbos directly prior to any Holiday including Rosh Hashanah. If however Rosh Hashanah falls on Shabbos, Vayehi Noam is recited the previous Motzei Shabbos.
Sparks of Chassidus
Hashem blesses this month:
On the Shabbos before Rosh Hashanah, which is the last Shabbos of the month of Elul, we read the passage in the Torah which begins נצבים אתם. These words are G-d’s blessing to the Jewish people. The Rebbe Rayatz records the following statement from his father the Rebbe Rashab: When I was a child I asked my father, the Rebbe Maharash, “Why do we not bless the month of Tishrei as we bless the other months?” The Rebbe Maharash in turn replied that when he was a child he had asked the same question to his father the Tzemach Tzedek who in turn said that when he was a child he asked this question to his grandfather the Alter Rebbe. The Alter Rebbe replied that he heard the following teaching in Mezritch from his master, the Maggid, who had received it from his master, the Baal Shem Tov: The seventh month [i.e. Tishrei], which is the first of the months of the year, is blessed by G-d Himself on Shabbos Mevarchim, which is the last Shabbos of the month of Elul. By virtue of this blessing the Jews are empowered to bless the other months eleven times a year. This is the content of G-d’s blessing: “Atem Nitzavim Hayom” [i.e. You are standing this day]. The word היום [i.e. this day] refers to Rosh Hashanah, which is the Day of Judgment. The phrase Atem Netzavim implies not only that the Jewish people are standing, but furthermore that on this day “you are sustained in your firm stance” which means that you are acquitted in your trial.
- The first night of Selichos is Motzei Shabbos. The custom is to begin Selichos immediately after midnight.
- On Motzei Shabbos, Selichos is said while still wearing one’s Shabbos clothing.
- It is customary to hold a Chassidic gathering on Motzei Shabbos in the hours prior to Selichos.
- One is to learn Torah prior to saying Selichos. The content to be learned is matters which pertain to practical Halacha. Likewise one is to study the Mamar of “Lecha Havayah Hatzedaka” [printed in the beginning of the Selichos] or at the very least its beginning and end. On the first night of Selichos this to be learned prior to midnight.
- One is to give charity prior to Selichos. On the 1st night of Selichos this is to be done only after midnight.
- The custom is to stand while reciting Selichos.
- The Chazan is to recite Selichos with a Tallis. If it is still before the allowable time to say a blessing over a Tallis the Chazan should borrow a Tallis from another person and wear it without a blessing.
- Selichos must be recited slowly and with concentration. It is better to recite a lesser amount of supplications, but with proper concentration, then a larger amount without concentration.
- It is forbidden to recite the thirteen attributes without proper concentration.
- One is to recite the 13 attributes with his back slightly arched forward.
At what hour of the day is Selichos to be recited?
The letter of the law: Selichos is to be said by “Ashmuras Haboker” [which corresponds to the last three hours of nightfall]. The reason for this is because the end of the night is a time when G-d discerns the matters of the world and thus this period of time is auspicious above.
The custom: Practically the custom today is to say Selichos before Shacharis, after Alos Hashachar. [The custom of the Rebbe was to recite Selichos in the morning much time after Ashmuros Haboker and sunrise. This is unlike the recorded custom in Sefer Haminhagim to recite Selichos by Ashmuros Haboker.]
The first night-Motzei Shabbos: On the first night of Selichos which is Motzei Shabbos the custom is to begin Selichos immediately after midnight.
Does one wear Shabbos clothes for Selichos of Motzei Shabbos?
On Motzei Shabbos, Selichos is said while still wearing one’s Shabbos clothing.
If Selichos could not be said before Shacharis may it be said later on?
If one could not say Selichos in the morning before Shacharis it may be said throughout the entire day, such as prior to Mincha.
The Chassidus of this Shabbos was heard with completely different concentration. On Friday night of Shabbos Selichos Chassidim would diminish their amount of sleep as they were unable to sleep. A person did not find his place. They would go to Mikveh prior to daytime. In the Mikveh they would meet many others hurrying on their way. It was recognizable that this Shabbos was different than every other Shabbos. In one’s mind passes the thought “To you Hashem is righteousness and to us is the face of shame”. One would immerse with a broken heart and question himself whether this is an immersion of true repentance or is he immersing with the rodent in his hand. When they would pass Binyamin’s Shtible they would hear the congregation saying Tehillim. The Tehillim of that Shabbos was also different then all the other Shabbasim.
It is customary to hold a Chassidic gathering on Motzei Shabbos in the hours prior to Selichos.
Selichos must be recited slowly and with concentration. It is better to recite a lesser amount of supplications, but with proper concentration, then a larger amount without concentration. Those that are accustomed to hastily recite the conclusion of Selichos are to nullify their custom.
Is one who is accustomed to immerse in a Mikveh to do so before or after Selichos?
One is to try to immerse in a Mikveh before Selichos. One who was unable to do so is [not to delay reciting Selichos with a Minyan and is rather] to immerse in a Mikveh after Selichos, before Davening.
Directives of the Rebbe related to Selichos:
Learning Torah: One is to learn Torah prior to saying Selichos. The content to be learned is matters which pertain to practical Halacha. Likewise one is to study the Mamar of “Lecha Havayah Hatzedaka” [printed in the beginning of the Selichos] or at the very least its beginning and end. On the first night of Selichos this to be learned prior to midnight.
Charity: One is to give charity prior to Selichos. On the 1st night of Selichos this is to be done only after midnight.
Must one stand during Selichos?
The custom is to stand while reciting Selichos. This especially applies when the ark is open, when the thirteen attributes are recited [and upon saying Ashamnu]. Nevertheless if it is difficult for one to stand, then he may be seated, with exception to when the thirteen attributes [and Ashamnu] is recited.
 Drasha of Rav: Some Poskim write the Rav is to give a speech on the Shabbos before R”H in order to arouse the people in repentance. This has support in the Midrash which states that when the Sage expounds the laws to the public Hashem forgives their sins. [Mateh Moshe 833; Kneses Hagedola 602/4; Elya Raba 603/2; Kaf Hachaim 602/10]
 Magen Avraham 417/1; Levush 421/1; 581/1; Mateh Efraim 581/47
 The reason: The reason for this is because the verse in Psalms states on Rosh Chodesh “Bikese Leyom Chageinu” which implies that Rosh Hashanah is to be concealed. Hence we do not announce the date of Rosh Chodesh which is the date of Rosh Hashanah. [Magen Avraham ibid] The reason we desire to conceal Rosh Hashanah is in order to confuse the Satan and prevent him from prosecuting against us on that day. [Levush 421/1]. The Rebbe explains that the Satan is confused by the lack of mentioning Rosh Chodesh as he now becomes even more convinced that the Jews are positive that their judgment has been sealed for good, and it is for this reason that they are not doing the Mitzvah of Rosh Chodesh. This hence weakens the Satan’s prosecution, being that he suspects that perhaps the judgment has already been secured. It also diminishes the Satan’s personal prosecutions as he sees that they are lacking the merit of Rosh Chodesh and hence a strong prosecution is not that necessary. Nevertheless in truth the above explanation does not suffice to justify annulling a custom of Jewry as practically we are now lacking the Avoda of Rosh Chodesh. Thus in truth the intent of not mentioning Rosh Chodesh is to arouse one in Teshuvah, so we become broken over the Mitzvah that was removed from us. It is this Teshuvah that is done due to feeling broken hearted that capsizes the Satan’s prosecution.[Likkutei Sichos 24 printed in Shaar Hamoadim Rosh Hashanah 5]
The Chassidic reason: See Sparks of Chassidus!
 Sefer Haminhagim p. 115 [English Edition]; Takanos of Rebbe Rayatz printed in Otzer Minhagei Chabad 81
 Mateh Efraim 581/47; Shaareiy Efraim 10/35; Toras Menachem 1990 4/299 [Sichas Netzavim Vayeilech; brought in Shaareiy Halacha Uminhag 5/68; Shulchan Menachem 3/75]
 The reason: Although on a regular Shabbos Mivarchim the paragraph of Av Harachamim is omitted, nevertheless since on this Shabbos the month is not verbally blessed in Shul therefore one is to recite this paragraph.
 This especially applies when this Shabbos is also Shabbos Selichos of which Chassidim were always accustomed to have a Farbrengen on this Shabbos. [See Hisvadyos 1951 2/327; 1982 4/2253; 1983 4/2045]
 Hisvadyos 1988 4/376
 295/3 regarding every Yom Tov; Mateh Efraim 581/47; See “The Laws and Customs of Motzei Shabbos” chapter 1 Halacha 4 further details on this subject!
 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 Beseiser 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]
 The reason: 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 they are not all fit for work 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. [Birkeiy Yosef brought in Shaareiy Teshuvah 295/2; Kaf Hachaim 295/9-10]
 So rules Admur ibid regarding all Holidays; M”E ibid regarding Rosh Hashanah; M”E 602/45 regarding Shabbos Shuva; See Otzer Minhagei Chabad p. 170 for difference in practice of the Rebbe over the years by Shabbos Teshuvah
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]
 Hayom Yom 25th Elul; Sefer Haminhagim p. 115 [English]
 Michaber and Rama 581/1; Sefer Haminhagim p. 114 [English Edition; There they mistakenly translated Ashmuros Haboker as dawn, in truth Ashmuros Haboker is before dawn].
 Bach 581; Perisha 581; M”B Hakdama 581; Piskeiy Teshuvos 581/2. Vetzaruch Iyun as from the M”B ibid it implies that it refers to the end of the last Ashmurah, and so is also implied from Admur Kama 1/8 that it is best to say Tikkun Chatzos by the end of any of the three Ashmuros as that time is auspicious above. [See Admur Kama 1/8 that there are 3 Ashmuros at night] Furthermore there is room to suggest that based on the ruling of Admur in the Mahadurah Basra regarding the auspiciousness of midnight over the time of Ashmuros, [this is the Kabalistic perspective which was not yet known in the times of the Shulchan Aruch] perhaps ideally Selichos is to be said every night by midnight and not by the last Ashmuros. Certainly one is allowed to say Selichos after midnight, before the last Ashmuros, if one is unable to say it by the last Ashmuros. [See Igros Moshe 2/105; Mishmeres Shalom 41/4; Piskeiy Teshuvos 581/2]
 G-d travels throughout 18000 worlds at night, and reaches this world by the [last] Ashmuros. [M”A 581/1 in name of Hagahos Maimanis brought in M”B in introduction to this chapter]
 Mateh Efraim 581/11; See Divrei Torah of Munkatch 1/76; Alef Hamagen 581/24
 Although by doing so one loses the auspicious time of Ashmuros Haboker, nevertheless since the entire period of Elul is auspicious there is a great advantage in saying Selichos even after Alos. This negates those that do not participate in Selichos under the claim that it is not taking place before Alos. [Alef Hamagen 581/24]
 This was the custom of the Rebbe Rayatz. See Otzer Minhagei Chabad Elul 55
 Sefer Haminhagim p. 114; This is the custom of majority of Ashkenazi Jewry [Piskeiy Teshuvos 581 footnote 15] This is a very old custom from earlier generations. [Igros Moshe 2/105] So was practiced by various Tzaddikim based on the Zohar. [Divrei Torah Munkatch 1/76]
The reason: It is our custom [Chabad] to say the Selichos immediately after midnight in living with the verse said in Selichos “Bemoitzaei Menucha”. [Sefer Haminhagim p. 114] This is done in order so one is able to say the Selichos with the happy mood that is still left over from Shabbos. [Leket Hayosher of student of Terumas Hadeshen brought in Piskeiy Teshuvos 581 footnote 15] The Rebbe explains the reason for this is because in truth the purpose of the Selichos is not merely to be forgiven for sin but that the sins turn to merits, which is a joyous occasion. This is hinted to in the Gematria of the word “Selach” which is 98, corresponding to the 98 curses brought in Ki Savo which are in truth disguised blessings that can be turned over to revealed blessing. [Shaar Hamoadim Elul 73]
The auspiciousness of midnight: The auspiciousness of this time is elaborated in the Zohar. As well the Talmud says that this is a time of appeasement above and that anyone who learns Torah at night the Shechina resides opposite him, and a “string of kindness” is drawn upon him for that day. One who does so is also called a servant of G-d. [Basra 1/3] The auspiciousness of the time of midnight is applicable at all times and in all places. [Basra 1/8] In the Mahadurah Kama [1/8], regarding Tikkun Chatzos, the time of “midnight” is not mentioned, [1/8] At the times of the Shulchan Aruch they still did not know of the greatness and auspiciousness of the time of midnight which is based on mainly Kabalistic sources, and thus in the first edition of the Shulchan Aruch of Admur he does not make mention of midnight. However in the second edition which follows more the Kabalistic rulings it is mentioned that midnight is the proper time of awakening. [See Machatzis Hashekel 1/4; Piskeiy Teshuvos 581/2].
Other Customs: There are communities which are accustomed to say Selichos on Motzei Shabbos by Ashmuras Haboker and not immediately after midnight. Nevertheless even they are accustomed to say it at night, as opposed to the other days when it is said by Alos. [Mateh Efraim 581/11] This is because in the first Selichos there is a stanza that discusses the night prayer. [Alef Lamateh ibid; See Aruch Hashulchan 581/4]
 Otzer Minhagei Chabad Elul 54 as the custom of the Rebbe. The Rebbe Rashab however would switch his Shabbos clothes immediately after Shabbos as stated there.
 Yechaveh Daas 1/46; Piskeiy Teshuvos 581/2; See Mateh Efrayim 581/11
 Likkutei Deburim Vol 1 page 151-158
 Admur Kama 1/9
 Birkeiy Yosef 581/5; Kaf Hachaim 581/6
 Reshimos Dvarim 1/326; Otzer Minhagei Chabad 4 [p.36]
 Shaar Hamoadim Elul 71-77; Sichos Kodesh 1974 2/435
 As charity is not given at night until midnight. [ibid]
 Shaar Hamoadim Elul 77; Hisvadyos 1982 4/4522;
 The number three in general holds auspicious meaning, as we see from the Talmud that matters relating to the Jewish people come in threes. [i.e. 3 levels of lineage; 3 parts of Torah etc.] The Rabbeim would therefore at times begin their Rosh Hashanah Mamarim on the 3rd day of Selichos.
 Mateh Efraim 581/18; Kitzur Shlah Miseches R”H “It is proper to stand while saying Selichos, and one who is unable to stand is at the very least to stand while reciting Keil Melech Rachamim and Vayavor and the 13 Middos”
 See Beir Moshe 1/23 regarding standing when the ark is open.
 See Admur 607/7 “One needs to confess standing and is hence not to lean in a way that it supports him from falling”.
 See Halacha D in Q&A!