Numbers 35:6-8

6“Six of the cities you give the Levites are to be cities of refuge, to which anyone who kills anyone may flee. Besides these, you are to give the Levites 42 more cities.

7In all, you are to give the Levites 48 cities with their pastures.

8The cities that you are to give to the Levites from the possession of Bnei-Yisrael should be proportionate to the inheritance of each tribe—give many from the one who has many and few from the one who has few.”