Joshua 21:3 - Matthew Poole's English Annotations on the Holy Bible

It seems most probable that they gave to the Levites promiscuously such cities as God commanded, and that the lot appropriated them to their several houses or families. Out of their inheritance, i.e. out of their several possessions; partly that the burden and loss might be equally divided and principally, that the Levites being dispersed among the several tribes, according to Jacob's prediction, Genesis 49:7, might more easily, and frequently, and effectually teach the Israelites God's law and judgments, which they were engaged to do, Deuteronomy 33:10; and that the people might upon all occasions resort to them, and require the meaning of the law at their mouths, Zechariah 2:7. These cities and their suburbs; not only the use, but the absolute dominion of them, as is manifest both from Joshua 21:11,12, where a distinction is made between the city and suburbs of Hebron, and the fields and villages thereof, and the former are given to the Levites, the latter to Caleb; and from the return of these cities in the jubilee unto the Levites, as to their proper owners, Leviticus 25:33,34.