Numbers 35:9-12

9And Jehovah spoke to Moses, saying,

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

11then ye shall appoint for yourselves cities: cities of refuge shall they be for you; that a manslayer may flee thither, who without intent smiteth a person mortally.

12And ye shall have these cities for refuge from the avenger; that the manslayer die not, until he have stood before the assembly in judgment.