Matthew Henry on Joshua 21:9-42

By mixing the Levites with the other tribes, they were made to see that the eyes of all Israel were upon them, and therefore it was their concern to walk so that their ministry might not be blamed. Every tribe had its share of Levites' cities. Thus did God graciously provide for keeping up religion among them, and that they might have the word in all parts of the land. Yet, blessed be God, we have the gospel more diffused amongst us. (Jos 21:43-45)