Matthew Henry on Joshua 21:1-8

The Levites waited till the other tribes were provided for, before they preferred their claim to Joshua. They build their claim upon a very good foundation; not their own merits or services, but the Divine precept. The maintenance of ministers is not a thing left merely to the will of the people, that they may let them starve if they please; they which preach the gospel should live by the gospel, and should live comfortably. (Jos 21:9-42)