By Rabbi Berach Steinfeld
In Vayikra 25:2, the Torah tells us that the land should rest in the seventh year as a Shabbos laHashem. In 25:4, the pasuk states that one may not plant or harvest. From here, we see that Shmitta consists of two mitzvos: one positive and one negative.
The Acharonim discuss whether the mitzvos of Shmitta are a personal obligation (gavra)—that a person may not work his field—or whether they are an obligation on the land itself (cheftza)—that the field must not be worked.
The Ramban and Even Ezra compare the mitzvah of Shmitta to Shabbos, explaining that just as every Jew must observe Shabbos, so too must every Jew observe Shmitta. This would imply that Shmitta is a mitzvah on the land (cheftza). However, the Rambam, in Hilchos Shemitta Veyovel 1:1, writes in his summary that the mitzvas aseh is that the land should rest during Shmitta, while the lav is that a person must not work his field during that year. It seems that the aseh is on the cheftza, while the lo saaseh is on the gavra. Nevertheless, the Rambam concludes by saying that one who works the field during Shmitta transgresses both a positive and negative commandment, which implies that the responsibility lies on the gavra.
The Gemara in Avodah Zarah 15b tells a story about Rav Huna, who sold a cow to a non-Jew. Rav Chisda questioned how he could do so, since one is not allowed to sell an animal to a non-Jew due to the concern that the animal might be lent back to the non-Jew and used on Shabbos. Rav Huna responded that there was a possibility the non-Jew would slaughter the animal to eat it, so the concern was not significant.
The Gemara then brings a proof from Beis Hillel that one is permitted to sell an animal to a Jew who does not observe Shmitta, since there is always the chance he may slaughter it. Rabba challenges this comparison: How can we equate Shabbos with Shmitta? On Shabbos, there is a mitzvah that an animal must rest, but during Shmitta, there is no such mitzvah regarding animals. Abaye responds that just as one can sell land during Shmitta—since the new owner may leave it fallow—one may also sell an animal even if there’s a chance it might be used improperly. Abaye’s statement suggests that the mitzvah of Shmitta is on the cheftza—the land.
Many Rishonim, including Rashi, agree that the mitzvah is on the cheftza. According to this view, one would not be permitted to rent out a field during Shmitta, since the land might be worked.
However, the Maharit disagrees with Rashi and the other Rishonim. He argues that if a non-Jew works a Jew’s field during Shmitta, the Jew only violates a derabbanan. The concern is merely maris ayin—it looks as if the work is being done for the Jew. Therefore, if the field is rented behavla’ah (e.g., a three-year lease at a fixed price), it would be permissible.
Rav Shlomo Zalman Auerbach similarly writes that one may rent an apartment with a garden to a non-religious Jew, even if there is concern he may work the garden during Shmitta, since it is only a derabbanan issue.
The Chazon Ish disagrees and deduces from Tosafos that the obligation of Shmitta is on the gavra. This leads to several nafka minas (practical differences):

• If someone else does the work on the land, whether there is a violation depends on whether the prohibition is on the gavra or the cheftza.
• When a field is rented, who has the mitzvah—the owner or the renter?
• If machines automatically perform agricultural work, whether that’s permitted depends on whether we consider it grama, and whether the issur lies on the person or the land.
• Another question is whether women are obligated in Shmitta. If the mitzvah is on the gavra, then it is a mitzvas aseh shehazman grama, from which women are typically exempt. If it’s on the cheftza, there would be no such distinction.
• In the case of jointly owned land, if only one partner works the land, are all partners in violation or only the one performing the work?
• A further nafka mina would be whether there’s value in purchasing land during Shmitta in order to leave it fallow. If the mitzvah is on the gavra, then the buyer would be fulfilling a chiyuv. If it’s on the cheftza, there would be no obligation.

Halacha lemaaseh, the consensus is that Shmitta is a hybrid: the aseh is on the cheftza, but the lo saaseh is on the gavra. Therefore, we are stringent in all of the above nafka minas.
May we be zocheh to fulfill the mitzvah of Shmitta in Eretz Yisroel through the redemption of Mashiach!
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