Six years you shall sow your field, and six years you shall prune your vineyard and gather in its fruits.
This possuk seems to command us to work the fields for six years. However, we know that there is no commandment to work the fields; rather, there is a prohibition against working the fields in the seventh year. Why does the Torah tell us to work the fields and gather the harvest?
The Ohr Hachaim explains the Halachic point of this possuk, that we are to learn that someone who works his fields during Shemittah has not only transgressed a prohibition but has also transgressed a positive command.
However, he adds other explanations to this. The Gemara in Bava Basra describes the method of planting a field, and we learn that it is normal to plant a field one year and leave it fallow the next year. This ensures that the nutrients are not depleted. If a person were to plant his field each year without a break, it would weaken its ability to produce anything, and the person would lose out. Planting a field for six years in a row is an agriculturally bad idea.
However, the Torah teaches us that a person who keeps Shemittah has a different agricultural system. He will plant his field for six years, and will still gather in its harvest. Nothing will change, even though he did not leave his field fallow as conventional advice would tell us.
He then offers another explanation, based on a Gemara. The Gemara tells us that Rabbi Yannai proclaimed: Go out and sow the fields during the Shemittah due to the arnona that you must pay. The farmers owed an arnona tax to the government, and they could not find a way out of it. Tosfos asks how they could permit a person to transgress a Biblical command when it was not a situation of physical danger. Tosfos answers that they were in physical danger because the government could punish them severely and dangerously if they did not produce what they were obligated to give them.
The Torah tells us that the prohibition against planting and harvesting in Shemittah is only when the purpose is וְאָׁסַפְתָׁ אֶת תְבוּאָׁתָׁהּ – you shall gather in its produce. If, however, the purpose is not to gather it in your warehouses, but rather to give it to the government for your taxes, the work is permitted.
