דברים טו:ט מקורות במשנה: Mishnah Sheviit

[A loan secured by] a prozbul is not cancelled. This was one of the things enacted by Hillel the elder; for when he observed people refraining from lending to one another, and thus transgressing what is written in the Torah, “Beware, lest you harbor the base thought, [‘The seventh year, the year of remission, is approaching,’ so that you are mean to your needy kinsman and give him nothing.” Hillel enacted the prozbul.