When the Jewish people live in Eretz Yisrael, each tribe in its portion, there is a mitzvah to observe every fiftieth year as Yovel (Sifra, Behar 1). One of the mitzvos associated with Yovel is that all fields in Eretz Yisrael return to their original owners in Yovel, and it is prohibited to sell a field permanently even to a fellow Jew. There is an additional law that allows a seller to “redeem” his field by repurchasing it from the buying after two years have passed. In the fiftieth year, a shofar is blown to prompt everyone to return whatever fields they purchased. Since it is hard for people to give up their property, it is necessary for the shofar blast to penetrate their hearts and prompt an instant and simultaneous collective relinquishment (Sefer HaChinuch).

Hashem explains: “The land may not be sold permanently because the land is Mind, and you are sojourners and tenants by Me” (Vayikra 25:23). In other words, Hashem wishes us to remember that our land is actually His and our residence there is dependent on His continued desire to allow us to stay, which is dependent on our worthiness. Our inability to purchase fields permanently reminds us of this fact and strengthens our resolve to be loyal servants of Hashem. An added benefit of this mitzvah is that it discourages theft and envy of property because people realize that whatever belongs to others is Divinely ordained (Sefer HaChinuch).

Yovel also serves to balance the financial standing of society. When people go through financial strain and are forced to sell their ancestral heritage, their loss becomes permanent, and on the opposite side of the scale, the wealthy amass property excessively. Hashem granted us financial security by limiting our ability to sell fields (Moreh Nevuchim Vol. 3 §39).

When a person sells a house, the Torah gives him the right to repurchase it even immediately. However, if the house is in a walled city, once a year passes from the time of the sale it becomes the permanent possession of the buyer, and it does notreturn in Yovel. If it is in an unwalled city, it may also be redeemed immediately, like a house in a walled city; however, it returns in Yovel, like a field.

The commentators explain that Hashem gives a seller the right to repurchase his house because it is difficult for a person to have to sell his house and it is shameful if circumstances force him to do so. Once a year has passed, during which the seller managed to live elsewhere, he no longer has the right to repurchase it. The year limit also encourages him to repurchase it. The Torah does not command the return of properties in Yovel except regarding fields because livelihood depends on them. Houses outside walled cities are generally built for farmers and watchmen. Since they are necessary for the upkeep of fields, they too return in Yovel (Ramban).

Another reason why the Torah allowed the permanent sale of houses in walled cities is to encourage the development of property, as people do not want to develop property that they own only temporarily. With regard to a field, on the other hand, it is common practice for a field owner to hire sharecroppers for short periods, and long-term consecutive ownership does not benefit the field's administration. Thus, the Torah applies the mitzvah to return fields during Yovel specifically to fields (Chizkuni).