Now, this is all very well for the Rebbeim themselves. As great and holy Tzaddikim who perceived spiritual realities, their distress at sleeping in the Sukkah was surely a tangible pain that justified their exemption from this otherwise obligatory practice. However, on what basis do their followers, regular people who do not sense sublime spiritual realities, choose to refrain from sleeping in the Sukkah?
The Rebbe explains:
Chassidim, since they are bound up with the Rebbeim of Chabad, study their teachings (with the goal of implementing them) and follow in their ways—the customs of their Rebbeim.Chassidim feel a very intense natural bond with their Rebbe, and this brings them to naturally strive to emulate their Rebbe’s conduct, even when that conduct may appear, or may even actually be, a lower standard in the strict sense. Emulating their Rebbe or otherwise declaring their adherence to their Rebbe is a hiddur in Hiskashrus, a beautification of the Mitzvah of connecting to one’s Rebbe, that is so significant that it overrides other otherwise valid halachic considerations.
This is along the lines of what the Gemara relates concerning Rav Acha, who would “beautify [the Mitzvah] with ‘two and one’”—by taking a myrtle branch with only “two leaves on one point and one leaf below, which rose up and covered the other two” (Sukkah 32b). This was consistent with the opinion of Rav Kahane [who had declared that it is permitted to use such a myrtle branch], despite the fact that Rav Kahane himself had only said that “one may even use [a myrtle branch of] ‘two and one’”; however, “three on one stem is certainly acceptable [i.e., the best manner of performing the Mitzvah].” However, “Since it went forth from the mouth of Rav Kahane,” his student regarded it as a hiddur [beatification] of the Mitzvah to make a point of acting according to Rav Kahane’s opinion. [The Rebbe goes on to explain an additional reason for not sleeping in the Sukkah.]
Elsewhere (Toras Menachem 5712, Vol. 5, p. 144 ff.), the Rebbe discusses this concept in connection with the Chabad custom on Pesach to avoid eating gebrochtz (Matzah mixed with water). On the first seven days of Pesach we are very particular not to let even the tiniest drop of water fall on Matzah in order to avoid even the smallest trace of gebrochtz. Yet on Acharon Shel Pesach (the last day of Pesach), not only did the Previous Rebbe not avoid gebrochtz, he would make a point of dipping the Matzah in every single dish.
“This conduct was surprising in my eyes,” the Rebbe says, until his attention was drawn to the above Talmudic statement concerning Rav Acha. Then, the Rebbe relates, he understood it: Since the Previous Rebbe had seen that his father, the Rebbe Rashab, would eat gebrochtz on Acharon Shel Pesach, he would make a point of eating gebrochtz on Acharon Shel Pesach as well—since it went forth from the mouth of his Rebbeim.
The Rebbe then stated that the above episode serves as a response to those who challenge various customs of chassidim, and cite various reasons for their arguments. Some examples are long farbrengens: Why waste so much time on a farbrengen? Why not toast L’Chaim, sing a niggun, finish the farbrengen in a half an hour, and sit down to learn Torah? Also, why do chassidim spend hours preparing for davvenen; why not prepare less, and davven at the proper time?
To this the Rebbe responded:
All the questions should be completely irrelevant, because we know that these are customs of chassidim [adopted because they were] either seen or heard from the Rebbeim.
It may appear to him that it will be better if he acts differently. For example, by davvenen in the proper time he will gain more time to learn Torah, and other such good things. Nevertheless, “Since it went forth from the mouth of Rav Kahane,” since he knows that this is the conduct of the Rebbeim, he should not seek [other] hiddurim. On the contrary, he should practice the hiddur of following their conduct—[as it says of Rav Acha, that] “He would beautify [the Mitzvah] with ‘two and one.’”
It is written, “According to the Torah that they will instruct you ... Do not stray from the thing that they tell you, to the right or to the left” (Devarim 17:11). This verse obligates us to follow the Beis Din of the generation (Mishneh Torah, beg. Laws of Mamrim) “even if they tells you about right that it is left, and about left that it is right” (Ibid. Sifri, Rashi). This applies to such an extent that even a student who has reached the point that he is worthy of ruling a matter of Jewish law, if he ruled that one should disregard the ruling of the Beis Din, he has the halachic status of a “rebellious elder” (Mishneh Torah, ibid. 3:4).
A similar principle applies in this case. Following Chassidic customs as taught by the Rebbeim is in the category of the obligation to follow “According to the Torah that they will instruct you” and “Do not stray from the thing that they tell you.” Thus, one should not seek [other] ways of beautifying the Mitzvah. Rather, the beautification ought to be—following the instruction of the Rebbeim.