The eightieth "cheder" in the palace of Hayom Yom.
Monday, 10 Adar I, 5703.
Shiurim: Chumash, Tetzaveh, sheni, with Rashi's commentary.
Tehillim, 10th of the month, from chapter 55 through and including chapter 59.
Tanya, chapter 29, from the word "vehasibah", until page 36, in the passage ending with the words "basar adam".
The daily teaching includes customs relating to birkas hamazon, and we will go through the list of customs that the Rebbe brings here. The heading is "In birkas hamazon" - all of today's customs deal with the subject of birkas hamazon. As is known, before birkas hamazon there is an order of several psalms that are recited: on a weekday, when Tachanun is said, one order of psalms is recited, and on a day when Tachanun is not said there are different psalms, and all of this comes before "mayim acharonim" at the end.
Right at the outset it is emphasized: "Before mayim acharonim one says Al Naharos Bavel, Lamnatzeiach Binginos, Avarcha, Zeh Chelek" - the entire list that the Rebbe brings from the custom that the Alter Rebbe brings in the Siddur, that before "mayim acharonim" all of this is recited. The novelty in this is that in a large portion of the writings of the Arizal and of the siddurim based on the Arizal it is written that all of these psalms should be said after "mayim acharonim", whereas the Alter Rebbe places all of this specifically before "mayim acharonim". After "mayim acharonim" the only thing recited is merely the conclusion of a verse, a few single words.
It may be that the reason is as the Alter Rebbe says in the Shulchan Aruch, that one should minimize matters so that there not be too long an interruption between "mayim acharonim" and birkas hamazon, and to bring the time of mayim acharonim as close as possible to birkas hamazon; and therefore, since the Alter Rebbe was concerned about an interruption, he placed all the psalms that are recited before "mayim acharonim".
Which is the first psalm recited every day? "Al Naharos Bavel", and as we will see shortly, on Shabbos one says the psalm "Beshuv Hashem es shivas Tziyon". The whole reason for this is built upon what is written in the Zohar, that a person who takes pleasure in his food and comes to thank Hashem for his eating - together with thanking Hashem for the food and being satisfied - must also remember Yerushalayim and feel pain over the destruction of the Mikdash. Therefore on a weekday one says the psalm "Al naharos Bavel sham yashavnu gam bachinu", which is fitting for a day on which Tachanun is said; and on Shabbos too one remembers the matter of Yerushalayim and the Beis Hamikdash, except that on Shabbos one says "Beshuv Hashem es shivas Tziyon" - for on Shabbos one speaks of the redemption, while on a day when Tachanun is said one mentions the matter of the destruction and the exile.
There is a sefer called "Seder Hayom", which brings a beautiful hint: the psalm preceding "Al Naharos Bavel" (chapter 137) in Tehillim is chapter 136, and at its end, one verse before its conclusion, it says "nosein lechem lechol basar ki le'olam chasdo", and immediately adjacent to it follows the psalm "Al naharos Bavel sham yashavnu". It is fitting, then, that we bless the Holy One, blessed be He, for the bread that He gives, and immediately afterward comes the psalm "Al Naharos Bavel". This is the hint in the joining of the two things.
The next psalm is "Lamnatzeiach Binginos", and after it the verses "Va'avarcha es Hashem" and the verse "Zeh Chelek". "Zeh Chelek" is a verse that is always said before birkas hamazon, both on a weekday and on Shabbos: "Zeh chelek adam rasha me'Elokim venachalas imro me'El". What is the matter of this verse? Its source is in the book of Iyov (chapter 20, verse 29), and the chapter there speaks in condemnation of the people of Sodom, particularly in matters of meals and hospitality, how corrupt they were. And it is known that "mayim acharonim" comes to remove the concern of melach sedomis; and from here the hint that before "mayim acharonim" this verse is recited, which in its source speaks of the negation of Sodom. This is the hint regarding the verse "Zeh Chelek".
All this is for birkas hamazon on an ordinary day. "On a day when Tachanun is said" - Shabbos, Yom Tov and the like - one says "Shir Hamaalos Beshuv" in place of "Al Naharos Bavel", and after it the second psalm, "Livnei Korach". "Avarcha" is said just as on a day when Tachanun is said, and "Zeh Chelek" too is the verse in which there is no difference between a day when Tachanun is said and a day when it is not said.
The conclusion of the teaching deals with what is said "after "mayim acharonim" "Vayedaber eilai zeh hashulchan asher lifnei Hashem". It is interesting that this is not a complete verse but only the end of a verse, in the book of Yechezkel. There is a description there of the mizbeach, and the verse begins with the measurements of the mizbeach and concludes with the words "Vayedaber eilai zeh hashulchan asher lifnei Hashem". Apparently the table upon which a person eats resembles the mizbeach, and therefore one says the conclusion of that verse in Yechezkel with these words: "Vayedaber eilai zeh hashulchan asher lifnei Hashem".