Numbers 35:6-8

6“Six of the towns you give the Levites will be cities of refuge, to which a person who has killed someone may flee. In addition, give them forty-two other towns.

7In all you must give the Levites forty-eight towns, together with their pasturelands.

8The towns you give the Levites from the land the Israelites possess are to be given in proportion to the inheritance of each tribe: Take many towns from a tribe that has many, but few from one that has few.”