Numbers 35:6-8

6And [among] the cities that ye shall give unto the Levites [shall be] the six cities of refuge, which ye shall appoint for the manslayer, that he may flee thither, — and besides them ye shall give forty-two cities:

7all the cities that ye shall give to the Levites shall be forty-eight cities, they and their suburbs.

8And the cities which ye shall give shall be of the possession of the children of Israel: from them that have much ye shall take much, and from them that have little ye shall take little; each one according to his inheritance which he will inherit shall give of his cities to the Levites.