The beginning of Parashat BeHar discusses the laws regarding Shemittah and Yoveil. The Torah states that for six years we should work the fields, and on every seventh year, we should stop working. The prohibitions of the seventh year are specifically against working the land. We know that from an agricultural standpoint, plowing the same land for too many years without giving it rest will make the land barren. Is it possible that the Mitzvah of Shemittah is specifically designed to prevent this, thereby physically benefiting our livelihoods? Moreover, the Torah gives a guarantee that if this commandment is kept, Hashem will provide us with financial success; therefore, the whole essence of this commandment seems to be for our physical (and financial) benefit! Is this truly so?
According to the Sefer HaChinuch, the Mitzvah of Shemittah is designed as a Shabbat for the ground, which humbles us and forces us to realize that Hashem provides us with the very land which we work and depend on for sustenance. Additionally, Shemittah demands trusting Hashem to provide us with food even though we refrain from plowing. However, one could say, maybe this is a primary explanation for the law of Shemittah; still, maybe a secondary purpose is that Shemittah is for our own benefit.
There is a fault with the very notion that Mitzvot are commanded to directly benefit us in this world. We cannot explain every Mitzvah in the Torah, so we cannot possibly anticipate the benefit of performing many Mitzvot. For instance, there is no logical explanation for Parah Adumah; how ash from a burnt red cow mixed with water can make one pure is beyond human comprehension. This is the classic example of the many Chukim in the Torah – laws which human reasoning simply cannot explain. If it is not possible to say that all Mitzvot are solely for our advantage, perhaps it may be suggested that some Mitzvot have secondary purposes just for this world, while some do not have any such advantages. Perhaps, this is why the section of the Tochachah, the rebuke, comes on the heels of the section about Shemittah. The theme of the Tochachah makes the whole issue clear. We must listen to Hashem and do His Mitzvot not because we realize that they will directly benefit us; on the contrary, we must always serve Hashem and perform His Mitzvot solely for the sake of serving God.