Numbers 35:6-8

6“The cities you give the Levites will include six cities of refuge, which you will provide so that the one who kills someone may flee there; in addition to these, give forty-two other cities.

7The total number of cities you give the Levites will be forty-eight, along with their pasturelands.

8Of the cities that you give from the Israelites’ territory, you should take more from a larger tribe and less from a smaller one. Each tribe is to give some of its cities to the Levites in proportion to the inheritance it receives.”