Prozbul פרוזבול

The Torah commands that debts be released at the end of the seventh year—and itself warns: do not refuse the poor a loan because the year of release is near. People refused. The rich stopped lending before the sabbatical year, and a commandment meant for the poor became their misfortune.

Hillel found the way out inside the law itself: the seventh year releases debts owed to a person, not to a court. The prozbul is the document by which a lender assigns collection to the court—and the debt survives the shmitah. It is the most famous case of the sages adjusting a law's application for the sake of its own purpose; the argument over the boldness of the step runs through the Talmud and has not died down. Prozbuls are written every shmitah to this day.