from his work
1. Pesach is the holiday of our freedom, celebrating our liberation from Egypt. By taking the Jewish people out of Egypt and later giving them the Torah at Mount Sinai, G-d created a new type of being; one that had never existed before, a being who is in essence free. After Sinai, the Jew may be exiled, persecuted and oppressed, but these will always be external conditions affecting only our external selves. The soul of the Jew can never be bent or even constricted. The soul remains forever united with G-d, and forever free.
(Gevurot Hashem 61)
2. Torah is a book of instructions. It is the how-to-connect-to-G-d book that Man was given at Sinai.
The first four books of Torah are the direct words of G-d. The fifth book, Deuteronomy, is comprised of words spoken by Moses, as dictated by G-d.
The first four books of Torah, then, are "closer to G-d" (on a philosophical level) than is the fifth. It is, in a way, as if G-d is placing Torah into the outstretched arms of Man, with Deuteronomy (the farthest end of Torah), reaching Man's arms first.
Torah contains both positive and negative commandments. Positive commandments are ways for us to connect with G-d. Negative commandments are ways for us not to distance ourselves from G-d. On a philosophical level, then, positive commandments are "closer to G-d" than negative commandments.
The Ten Commandments are listed twice in Torah; first in Exodus (the second book of Torah) and later in Deuteronomy. Interestingly, Shabbat is mentioned as a positive commandment (zachor) in the Exodus listing and as a negative commandment (shamor) in Deuteronomy.
Because, as Exodus is in the section of Torah "closer to G-d," Shabbat is listed there in a way that is "closer to G-d": a positive commandment.
Deuteronomy, located in the part of Torah "closer to Man," mentions Shabbat in a way that is "closer to Man" too: a negative commandment!
(Tiferes Yisroel; chapters 43-44)
3. The Talmud (Shabbos 88A) states: "At [G-d's] revelation [to the Jewish People] at Mt. Sinai, G-d picked up [the mountain] and held it over the Jewish People's heads, and said: If you accept the Torah all is well, but if not, you will be buried beneath this mountain."
This is perplexing. The Jews had already willingly accepted the Torah, exclaiming "We will do and only then will we hear," (Exodus 19:8) expressing a total devotion to Torah.
Why, then, was it necessary for G-d to force the Jewish People to accept Torah, something they had already accepted?
The Jewish People are G-d's "Ambassadors of Spirituality" to mankind. They are a body that is charged with teaching humanity spirituality and G-dliness. They do this by keeping Torah.
Jews and Torah, then, have to be totally connected.
Had the Jewish People voluntarily accepted Torah, their relationship to Torah would have been weak: it would have appeared as a relationship of preference.
A stronger connection was needed.
Thus G-d forced the Jews to accept Torah. The bond of commandment is beyond any unsteadiness that may lie in the realm of choice.
(Tiferes Yisroel; Chapter 32)
4. On the first day of Adam's creation, G-d gave him six basic mitzvot. Noach, ten generations later, was given a seventh commandment (the prohibition against dismembering and eating live animals). Abraham, ten generations after that, was given another commandment (circumcision). Yaakov, two generations later, was given an eighth commandment (the prohibition against eating animals' sciatic nerve).
Torah in its entirety was only given to the Jewish People much later: in the year 1948 [from creation], after the Jews had left Egypt and become a nation.
Clearly, Torah in its entirety could not have been given to Adam or Noah - as Torah is not intended for all humanity.
Why, though, was Torah not given to our patriarchs: Abraham, Isaac, and Jacob?
Torah is a supernatural entity that can never be altered and can never be changed. Thus, Torah, can only be received by an entity that, also, will exist forever.
Abraham, Isaac and Jacob were sublime and totally spiritual people - and the founding force of our nation. Yet their identities were individual - and limited to their lifetimes.
Only when the Jewish people reached nationhood - and received the eternal name "Israel" - did an eternal entity exist that could receive the eternal Torah.
(Tiferes Yisroel; Chapter 17)
5. Midrash (Mishlei chapter 9) says that at the time of resurrection (i.e. the end of days,) the Jewish People will no longer celebrate the holidays that it celebrates today.
There will, however, be exceptions to this rule. Purim and Yom Kippur will be celebrated.
Why are these two holidays different? Why will they endure?
Purim celebrates our national survival from a death-decree. G-d saved us, then, after King Achashverosh had already signed and sealed our fate to doom.
Yom Kippur, too, is of this nature. On that holiest of days, while our sins warrant that G-d end our physical existence, G-d gives us a renewed "license to live."
This is the very theme of resurrection. Resurrection will be a time when we will receive life from G-d, after our physical existence has ended.
Thus, Purim and Yom Kippur will be celebrated at the end of days, as they are so similar to the nature of that time.
(Tiferes Yisroel; Chapter 53)