Cf. Siddur, p. 368-371

(a) “The Nasi”:

[Every day from Rosh Chodesh Nissan until the twelfth of the month, usually after Shacharis,] one reads the passage [from Bamidbar 7-8:4] that describes the offering brought on that day by a particular Nasi, or tribal prince, for the dedication of the altar of the Mishkan. [In common parlance, each day’s passage itself is often referred to as “the Nasi.”] This daily reading is followed by the prayer which opens with the words יהי רצון (and which appears in Siddur Torah Or [as well as in Siddur Tehillat HaShem, p. 371]). This prayer is recited even by a Kohen or a Levi [despite its seeming relevance only to tribes other than the Tribe of Levi].1

(b) Beis Nissan:

The second of Nissan is the yahrzeit of [the fifth of the Rebbeim of Chabad,] Rabbi Shalom DovBer — the Rebbe Rashab [5621 (תרכ"א; 1860) — 5680 (תר"פ; 1920)].

“The Rebbe Rashab passed away at about 4:30 a.m. on Motzaei Shabbos Parshas Vayikra, before daybreak on the second of Nissan, 5680, in Rostov [on the River Don], and his resting place is there.”2

“At about twenty minutes after four, with the approach of dawn on the second day of the first month, the highest heavens opened up, and the pure soul ascended — to pour itself forth into its Father’s bosom. With a holy sweetness, with a noble tranquillity, our holy master handed over his soul to G‑d, the L‑rd of all spirits.”3

(c) Yud-Alef Nissan:

The eleventh of Nissan is the birthday of the seventh of the Rebbeim of Chabad, Rabbi Menachem Mendel Schneerson — the Lubavitcher Rebbe Shlita, who was born in 5662 (תרס"ב; 1902), and assumed the mantle of leadership in 5710 (תש"י; 1950).4 May he be blessed with long and happy years!

(d) Yud-Gimmel Nissan:

The thirteenth of Nissan is the yahrzeit of the third of the Rebbeim of Chabad, Rabbi Menachem Mendel — the Tzemach Tzedek, who [was born in 5549 (תקמ"ט; 1789) and] assumed the leadership in 5588 (תקפ"ח; 1827).5

“Moreover, we must inform you of the passing of our holy master during the night preceding Thursday, the thirteenth of Nissan, 37 minutes after ...6 a.m.”7

This was in 5626 (תרכ"ו; 1866); his resting place is in the village of Lubavitch.

(e) Shabbos HaGadol:8

The Haftorah beginning וערבה (Malachi 3:4-24) is read only when Shabbos HaGadol falls on erev Pesach. This passage tells of the tithe that was to be brought to the storehouse [of the Beis HaMikdash], and the time for clearing one’s home of tithes (in the fourth and seventh years of the Sabbatical cycle) was erev Pesach.

Following the ruling of the Shulchan Aruch, end of sec. 430, after Minchah on Shabbos HaGadol we read part of the Haggadah, from עבדים היינו until לכפר על כל עונותנו, because the redemption and the miracles began on the Shabbos before Pesach.9

(f) The Sale of Chametz:

It is not the custom in the Rebbe’s household to make the rav an agent for the sale (mechiras chametz); rather, the leaven is sold to him outright, with an areiv kablan, a third-party guarantor.10

(g) The Search for Chametz:

The search for leaven (bedikas chametz) takes place after Maariv.11

It is customary in the Rebbe’s household to place ten pieces of hard bread in various places, each wrapped in paper.

One searches by the light of a beeswax candle (Shulchan Aruch, sec. 433) and with a feather. The chametz found is placed in a small paper bag. After the search one places the bag, together with the feather and any remnant of the candle, in a wooden spoon. All this is then wrapped in paper (except for the spoon handle which remains uncovered), and bound several times with string, which is then knotted.

(h) Erev Pesach:

From the morning of erev Pesach until after the korech of the Second Seder it is our custom not to eat any of the ingredients of the charoses or maror.

“Some time after writing the above,” [notes the Rebbe Shlita,] “I read that certain people are accustomed not to eat chazeres [for a certain time] before Pesach, and that this was the custom of the Rashba.”

(i) Shemurah Matzah:12

The Rebbe Shlita has asked everyone, especially rabbanim, shochatim and anyone else involved in communal activities, to endeavor to distribute round, hand-baked matzos — specifically shemurah — to their acquaintances, sufficient for at least both Sedarim. People organizing communal Sedarim, in hotels and the like, should also attend to this.13

The Rebbe Rashab used to be present at the baking of shemurah matzah after midday on erev Pesach. He would join in the Hallel, interrupting his recitation — even in the middle of a chapter — to direct the kneading, baking, and so on.14

It is the custom of the Rebbe Shlita to distribute shemurah matzah after Minchah on erev Pesach, at which time he wears the silk surtuk (frock coat) of Shabbos and Yom-Tov, and a gartl.15

(j) Friday Evening:

When Shabbos coincides with a Yom-Tov or Chol HaMoed, the last stanza of Lechah Dodi reads גם בשמחה ובצהלה.

When a Yom-Tov or Chol HaMoed coincides with Shabbos, the following passages are said in a whisper: שלום עליכם, אשת חיל, מזמור לדוד, דא היא סעודתא.16

(k) Festive Joy:

Though the Torah17 ordains that one should rejoice on Yom-Tov, one should certainly not become intoxicated, and the like; as Rambam writes with regard to simchas Yom-Tov, “One should not over-indulge in wine18 and so on.”19

(l) Pesach Etiquette:

Rabbi Chayim Avraham (son of the Alter Rebbe) once visited his brother, the Mitteler Rebbe (Rabbi DovBer of Lubavitch), to wish him a good Yom-Tov. On that occasion he related that the Alter Rebbe had once said: “On Pesach one does not offer a visitor food and drink, but the visitor may help himself.”20

(m) Kerias Shema:

On the second night of Pesach, the Prayer Before Retiring at Night follows the same order as on any other festival.21