Numbers 35:3-4

35:3 Thus they will have towns in which to live, and their grazing lands will be for their cattle, for their possessions, and for all their animals. 35:4 The grazing lands around the towns that you will give to the Levites must extend to a distance of 500 yards from the town wall.

Numbers 35:7

35:7 “So the total of the towns you will give the Levites is forty-eight. You must give these together with their grazing lands.

Numbers 35:12

35:12 And they must stand as your towns of refuge from the avenger in order that the killer may not die until he has stood trial before the community.