Shevi'it is the fifth tractate of Seder Zeraim of the Mishnah, dealing with the laws of leaving the fields of the Land of Israel to lie fallow every seventh year; the laws concerning which produce may, or may not be eaten during the Sabbatical year; and the cancellation of debts and the rabbinical ordinance established to allow a creditor to reclaim a debt after the Sabbatical year. Wikipedia