Deuteronomy 19:4-7

4This is the rule when anyone has killed another person: If it was a mistake, he can run to a safe city. He can do that if he has killed someone that he did not already hate.

5For example, two men may go to the forest to cut wood. As one man cuts wood with his axe, the metal part of the axe flies off. It hits the other man and it kills him. Then the killer can run to the nearest of the three cities. He will be safe there.

6If there was no safe city near enough, the killer might not escape safely. The dead person's relative might chase him, catch him and kill him. But the killer did not deserve to die. He had made a mistake. He had killed someone that he did not already hate.

7So I command you to choose three cities to be safe cities for yourselves.