Shemitah is not only about agriculture. Loans are also cancelled out by the end of the shemitah year. In addition to the agricultural laws of shemitah that we learn about in Parshat Mishpatim and in Parshat Behar, in Parshat Re’eh (Dvarim 15:1-10) we learn about Shmitat Ksafim (cancelling debts):
At the end of seven years you shall institute a remission. This is the matter of the remission: every creditor shall remit his authority over what he has lent his fellow; he shall not press his fellow or his brother for He has proclaimed a remission for God. You may press the gentile; but over what you have with your brother, you shall remit your authority…Beware lest there be a lawless thought in your heart saying, “The seventh year approaches, the remission year,” and you will look malevolently upon your destitute brother and refuse to give him- then he may appeal against you to God and it will be a sin upon you. You shall surely give him and let your heart not feel bad when you give him, for in return for this matter, Hashem, your God will bless you in all your deeds and in your every undertaking.
Is Cancellation of Debts D’Oraita (a Biblical obligation) or D’Rabbanan (a Rabbinic Obligation) today?
Hillel instituted prosbul (a document that allows debts to be collected after shemitah) for the benefit of society (Talmud, Gittin 36a).
We learn in the Mishna (Shviit 10:3-4):
When a person writes a prosbul, he does not have to relinquish his loans and may collect them after shemitah. This is one of the things that Hillel HaZaken instituted for he saw that the people refrained from lending money to one another as shemitah approached because they were afraid that they would not be repaid in time. They thereby transgressed that which is written in the Torah (Dvarim 15:9): “Beware lest there be a lawless thought in your heart saying, “The seventh year approaches, the remission year,” and you will look malevolently upon your destitute brother and refuse to give him…” Hillel therefore rose and instituted prosbul.
The Gemara asks: Is it possible that from a Biblical standpoint, the seventh year cancels loans yet Hillel decreed that it does not cancel?
The Gemara answers: Abaye said: Hillel instituted prosbul to be effective only in regard to the observation of shemitah nowadays, following the view of Rebbi, that shemitah’s cancellation of loans nowadays is only a rabbinic law. As it was taught in a Braita: Rebbi says “and this is the matter of the remission, remit”. The verse speaks of two shemitot (relinquishments) one is the relinquishment of land (shemitah of the land) and one is the relinquishment of monies (Shmitat Ksafim) that are owed to you. The Torah compares the two to teach us that at a time that you relinquish land, you relinquish monies that are owed to you. But at a time that you do not relinquish land, you do not have the obligation to relinquish monies.
Abaye continues: Nevertheless, the Rabbis declared that shemitah should cancel out loans even nowadays, as a reminder of the Biblical law of the seventh year so that it will not be forgotten. Since shemitah’s cancellation of loans became Rabbinic, when Hillel saw that people refrained from lending money to one another, he rose and instituted the prosbul.
The Rambam, Rashi, Rabbeinu Tam, Rashba and Ritva all follow the view of Rebbe and Hillel that Shmitat Ksafim is Rabbinic today.
How does the Prosbul work?
The lender authorizes a Beit Din (a court of three observant men) to collect money on their behalf. Only loans between a Jew and their fellow Jew are cancelled (not loans between a Jew and a Beit Din) as we learn in Dvarim 15:3, “You must forfeit a claim against your brother.”
We see that shemitah is not only about agriculture, it is also about loans being cancelled out by the end of the shemitah year. If you lent out money which you would like to get back, then you should set up a prosbul!