NUM 35:25

25 [If they decide that the killer planned to kill the other person, they must not allow him to stay in their city. But if they decide that it was done accidentally], they must protect the killer from being killed by the dead person’s relative. They must send the killer to one of the cities where he will be safe/protected, and allow him to stay there until the Supreme Priest dies. [After that, the killer may go back to his home, because the dead person’s relative no longer has the right to get revenge].