Numbers 35:6-8

“Six of these towns that you give the Levites will be asylum-cities to which anyone who accidentally kills another person may flee for asylum. In addition, you will give them forty-two other towns—forty-eight towns in all, together with their pastures. The towns that you give the Levites from the common inheritance of the People of Israel are to be taken in proportion to the size of each tribe—many towns from a tribe that has many, few from a tribe that has few.”