Sukkos
Regarding what the Alter Rebbe writes in his Shulchan Aruch, Orach Chaim, section 639, paragraph 13, that one repeats the blessing on the sukkah if he did not return immediately but only after one or two hours; whereas in section 25, paragraph 29, regarding tefillin, he writes "after a lengthy time, such as two or three hours." [The questioner] asks the reason for the distinction between sukkah and tefillin. Also — [OCR unclear] (b) why does he add afterwards "or two" (or "three")?
Now, this was already addressed in the sefer Ketzos HaShulchan by Rabbi Avraham Chaim Naeh, in the laws of tefillin, in Badei HaShulchan, subsection 63 [OCR unclear]. He cites the words of Rashi on Yoma (30a), s.v. "Notel," that since he delayed one or two hours, he has diverted his mind from his meal. And in the Siddur of Rabbi Yaakov Emden (Ya'avetz), in the laws of tefillin, he writes, regarding returning and reciting the blessing on tefillin: two or three hours.
He concludes — in Ketzos HaShulchan — that there is no logical basis whatsoever to distinguish between tefillin and sukkah; moreover, if two [hours] is considered a lengthy time, then all the more so three. And he leaves the matter as requiring great study.
What appears to me, in my humble opinion, on this: First, to amplify the question — we find four distinctions in the above: 1) Sukkah — one or two hours. 2) Tefillin — two or three hours. 3) Tzitzis — after several hours (the Shulchan Aruch of our Rebbe, section 8, paragraph 23, and in his Siddur). In Badei HaShulchan, section 7, subsection 17, he remarks on this: two or three hours is what is called a lengthy time in section 25, paragraph 29. But from the change in the Alter Rebbe's wording here it is implied [OCR unclear] that this is the measure.
[OCR unclear] Sukkah — its main establishment is [OCR unclear] (see section 639 [OCR unclear]). Tefillin — [OCR unclear] most people [OCR unclear] (since [OCR unclear] all day, for he now removes them [OCR unclear]), or the time of prayer (see Shulchan Aruch [OCR unclear] section 27, and section 25 [OCR unclear]). Tzitzis (a tallis gadol [OCR unclear]) — its time is fixed; but it extends longer than tefillin, since he puts it on before [OCR unclear], and it does not require a clean body, and there is no need of care regarding a diversion of the mind (see Shulchan Aruch, section 8 [OCR unclear]). One may say that since the person has separated [OCR unclear], the [OCR unclear] is interrupted upon his entry. Or, conversely, since [OCR unclear] a short time, there is in general no [OCR unclear] interruption in this.
Now, the duration of an ordinary meal — one may say it is one hour. A support for this [OCR unclear] from the saying of our Sages (Berachos [OCR unclear]a) that the meal (the regular one, twice a day) [OCR unclear]; and it is stated (Pesachim 58a) that the offering of the Tamid (the regular offering, twice a day) lasted one hour [OCR unclear]; and see what our Sages said (Shabbos 10a) [OCR unclear] hour [OCR unclear] the first hour. And note [OCR unclear] (b), "at four hours," and Rashi explains [OCR unclear] the meal.
Now, this measure [applies to] an ordinary meal. But [OCR unclear] our Sages said that one should prolong [one's stay] at his table (Berachos [OCR unclear]); and since it was extended beyond one hour, they established it at two — for those who prolong. One may say that this is [what] Rashi [intends] (Yoma, as above) [OCR unclear] (see also [OCR unclear] on the Rif, end of chapter 8 of Berachos). The time of prayer (including putting on and removing the tefillin, [Pesukei de]Zimrah, etc.) is more than an hour and a half [OCR unclear] (see [OCR unclear]) [OCR unclear]. And [as a] segulah for length of days, our Sages said (Berachos [OCR unclear]) to prolong one's prayer; so, as above, since it was extended beyond two [hours], they established it at three — for those who prolong. Thereby all the above measures are explained.
And note from Berachos (32b) that the early pious ones would [OCR unclear] in their prayer. And in Pri Etz Chaim, Gate of Prayer, chapter 1 [OCR unclear], it is explained that although the impression of the mochin [remains] all day [OCR unclear], the mochin themselves cannot be retained for more than three hours.
[OCR unclear] in the middle of the meal [OCR unclear], for although the meal is a mitzvah, he has already fulfilled his obligation.
As for what he asks from the Alter Rebbe's Shulchan Aruch [OCR unclear] — [OCR unclear] an addition after a time [OCR unclear].
[OCR unclear] permitted (Tanya, chapter [OCR unclear]) [OCR unclear].
Key Lesson
The differing time-spans the Alter Rebbe gives for repeating a blessing — one or two hours for the sukkah, two or three for tefillin, several hours for tzitzis — are not arbitrary: each reflects the natural length of the activity tied to that mitzvah, with the larger figure for those who prolong it. This Sicha shows how carefully every word of the Alter Rebbe's rulings is measured, and that even a meal or a prayer, lengthened for the sake of Heaven, is given its own standing in halachah.