Numbers 35:10

⁸  And the cities which ye shall give shall be of the possession of the children of Israel: from them that have many ye shall give many; but from them that have few ye shall give few: every one shall give of his cities unto the Levites according to his inheritance which he inheriteth.

⁹  And the LORD spake unto Moses, saying,

¹⁰  Speak unto the children of Israel, and say unto them, When ye be come over Jordan into the land of Canaan;

¹¹  Then ye shall appoint you cities to be cities of refuge for you; that the slayer may flee thither, which killeth any person at unawares.

¹²  And they shall be unto you cities for refuge from the avenger; that the manslayer die not, until he stand before the congregation in judgment.