Another example of tikkun ha-olam that appears in the Mishna is Hillel’s establishment of a prosbol. Aside from the agricultural laws connected with the Sabbatical year, the Torah also commands that all debts are annulled, with the law known as shemitat kesafim. The prosbol document effectively turns over all debts to the courts so that the individual creditor will not be collecting – which would be forbidden after shemita – rather the court, which is not obligated in this law, will be collecting the debts.
This enactment was established by Hillel in order to ensure that loans would be available to the poor even just prior to the shemita year. Observing that many people refused to lend when they feared that the loan would not need to be repaid, Hillel expressed concern that the commandment to make loans available at all times would go unfulfilled (see 15:9). By establishing prosbol, Hillel avoided this problem.
The mechanics of the enactment are subject to some disagreement. According to the Sifre it appears that the law annulling debts during shemitah applies only to the creditor, but not when the loan was turned over to the court. Hillel’s legal document allowed the debt to be taken over by the court without the promissory notes actually changing hands. Another approach is that the law of shemitat kesafim applies even if the loan is turned over to the court. What the prosbol accomplishes is effectively adding a condition to the loan allowing it to be collected “tenai she-ba-mamon kayyam” – that in money matters any agreed upon condition applies, even if it negates the standard rules as presented by the Torah.