But the field of the suburbs of their cities may not be sold. — The Levitical cities had both suburbs or commons for their cattle, &c, and fields which they cultivated (Numbers 35:4-5). These outlying fields, which were beyond the suburbs, they are here forbidden to sell. According to the authorities during the second Temple the expression “to sell” here used is to be taken in a wider sense as including diverting any part of it from its original purpose. Hence they say it forbids the Levites not only to sell the field, but to convert it into a suburb, and vice versâ. 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 to all futurity, and the present occupiers have to transmit them intact to their successors. Hence 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.