The fifth aliyah has additional laws of selling real estate with respect to the Jubilee year. Here, the Torah discusses houses in walled cities (like Yirushalayim) which can be redeemed by their sellers for up to a year after the sale, and if not redeemed in that year, become the permanent property of the buyer, and they are not released by the Jubilee. An exception to this is when a member of the tribe of the Levites sells his house in one of the cities of the Levites, the Levite shall always have the power to redeem it, and it will be redeemed by the Jubilee.
This aliyah then turns to the matter of helping one another; we are told that when one of our brethren becomes impoverished, we must come to his aid. And this is where we are told that a Jewish lender may not charge interest to a Jew. In fact, the Jewish borrower is independently forbidden to pay interest to a Jew. (For business purposes, there is a mechanism called Heter Iska - "permission to business", which both partners sign, and permits certain transactions.)
