Mishnayos Sheviis Perek 10 Mishnah 3

פרוזבול אינו משמט – The word פרוז is an ordinance (for the public welfare) (see comment of Rav Hisda in Talmud Gittin 36b); the word בול is for the rich (and Rashi’s commentary at the top of Talmud Gittin 37a), as it written (Leviticus 26:19): “And I will break your proud glory. [I will make your skies like iron and your earth like copper].” And Rav Yosef (see Talmud GIttin 37a) stated that these are the cities in Judea. An ordinance was made for the rich that they would not transgress on [the verse] (Deuteronomy 15:9): “Beware lest your harbor the base thought, [‘The seventh year, the year of remission, is approaching’],” and there is an ordinance for the poor that they would find someone who will lend to them, for the cancelling of cash debts in the present time is Rabbinic, as it is written (Deuteronomy 15:2): “This shall be the nature of the remission: every creditor shall remit the due that he claims from his fellow…,” as the Biblical verse speaks of two remissions: one is the remission of land and one is the remission/cancellation of cash debts, for at the time when one remits/cancels land debts, you remit/cancel cash debts, and at the time when you don’t remit land debts, you don’t remit/cancel cash debts; and it is Rabbinic, for they ordained the cancellation of cash debts at this time, and because of this, there was power in the hand of Hillel to establish Prozbul to cancel/release the law of remission, for the cancellation of cash debts is none other than from the words of the Scribes.