Rashi, commenting on the opening Posuk of this week's Parsha (ויקרא כ"ה;א'), asks "מה ענין שמיטה אצל הר סיני," "Why is (the law of) Shemittah especially associated with Har Sinai?" He is referring to the fact that the Torah (שם) specifically states that the laws of Shemittah presented here were given at Har Sinai. But as Rashi (שם) says, "הלא כל המצוות נאמרו מסיני," indicating that indeed all the Mitzvos were given at Har Sinai. Why should the Torah suddenly single out this Mitzvah and tell us that it was given at Har Sinai? Rashi then responds that the Torah is teaching us that just as with regards to Shemittah, all the particular rules and details are itemized, as outlined in our Parsha, as a part of what was actually said at Har Sinai, so too all the particular rules and details of all the Mitzvos were spelled out at Har Sinai, even where the Torah might not specify them clearly.
This statement of Rashi is an eye-opener, for the answer doesn't seem to fully respond to the question. We can, of course, understand why the Torah would want to describe one Mitzvah in great detail in order to teach that all the Mitzvos were given at Har Sinai. But the Torah could have spelled out the particulars of Shabbos, or Tefillin, or Tzedakkah, or any other Mitzvah, and we would also have been able to conclude from there that all the specific nuances of all the rest of the Mitzvos were transmitted by Hashem at Har Sinai. Why, then, does the Torah single out Shemittah?
There are in fact deep and special reasons why Shemittah was showcased to be the model for all other Mitzvos in this regard. Rav Yitzchak Breuer develops this approach to this Parsha in the following way, as presented by Rabbi Yehudah Nachshoni (ספר הגות בפרשיות התורה לפ' בהר). The observance of the Shemittah relating to the natural phenomenon of vegetation and agriculture is clearly a statement recognizing Hashem's dominion not only in the area of נסים ונפלאות, miracles and wonders, but also in the very core of nature itself. One who adheres to the laws of Shemittah thus bears witness to the sanctity of Hashem in all areas, especially nature. There is nothing in the world with which Hashem is not involved. Shemittah therefore teaches us never to take any thing for granted, and to recall that everything, even what we call nature, exists only by the will of Hashem. Moreover, Rabbi Shmuel Kushelevitz in his Sefer נתיבות שמואל, underscores the issue of בטחון, faith in Hashem, as a trademark of the Mitzvah of Shemittah, since only with true faith will one be ready to go for a whole year without working the fields. These two ideas together, namely, faith in Hashem and realization of His role in even the natural areas of life's functions, combine to provide a vital model which all other Mitzvos can develop from. Once one has focused on Shemittah, and understood its significance, one can apply its lessons to other Mitzvos. This is why specifically Shemittah is singled out to be connected to Har Sinai.
How often many of us forget that Hashem controls not only the phenomenal and supernatural activities of the world, but also, and indeed especially, the basic fundamental processes of life itself. It is therefore very clear why the Shemittah year is labeled as a year of Shabbos (שם פסוק ו'). Shemittah represents בטחון and the recognition of Hashem's presence and His Kedushah for an entire year, just as Shabbos allows us to recognize this every week.
This lesson in faith and recognition of Hashem is actually what true freedom is all about, because freedom from oppression should enable us to see the greatness of Hashem even more clearly. But somehow, this lesson has not been learned. We in the United States live in the greatest country in the world, both today and in the history of humanity. And yet, much of what Hitler and the Nazis ימח שמם tried to accomplish in the Holocaust in terms of eliminating the Jewish people, we are doing ourselves in this very country through assimilation. In the United States we are free to desecrate Shabbos, we are free to eat non-Kosher food, we are free to intermarry, and we are free to violate all of Hashem's Mitzvos. We have misunderstood how to use freedom. But when 56% of American Jews have intermarried, we will have lost over fifty to sixty years more Jews than in all the concentration camps of Europe. We here in the United States are eliminating ourselves; not physically, of course, but as Jews. We must thus decide to use our freedom here properly and learn the lessons of Shemittah. We must return to our faith in Hashem and to our commitment to Sinai. This is the proper expression of freedom, and more important, this is the guarantee that the Torah and Judaism will live on forever.