Charles Ellicott Commentary Leviticus 25:34

"But the field of the suburbs of their cities may not be sold; for it is their perpetual possession." — Leviticus 25:34 (ASV)

But the field of the suburbs of their cities may not be sold. —The Levitical cities had both suburbs, or commons for their cattle, etc., and fields which they cultivated (Numbers 35:4–5). These outlying fields, which were beyond the suburbs, are here forbidden to be sold. According to the authorities during the Second Temple, the expression “to sell” used here is to be understood in a wider sense, as including diverting any part of it from its original purpose. Therefore, they say, it forbids the Levites not only to sell the field but also to convert it into a suburb, and vice versa. What is field must always remain field, what is suburb must remain suburb, and what is city must continue to be city.

For it is their perpetual possession. —The estates belong to the whole tribe in perpetuity, and the present occupiers must transmit them intact to their successors. Therefore, no present owner, or all of them combined, have a right to dispose of any portion of the estates, or materially to alter it. They must hand these estates down to their successors as they receive them from their predecessors.