Leviticus 25:34,35

The field of the suburbs (namely, of the cities of the Levites) may not be sold Not at all; partly, because it was of absolute necessity for them for the keeping of their cattle, and partly because these were no enclosures, but common fields, in which all the Levites that lived in such a city had an interest, and therefore no particular Levite could dispose of his part in it. A sojourner Understand it of proselytes only, for of other strangers they were permitted to take usury, Deuteronomy 23:20.