Numbers 35:27

24 Then the congregation shall judge between the slayer and the avenger of blood according to these judgments:

25 And the congregation shall deliver the slayer out of the hand of the avenger of blood, and the congregation shall restore him to the city of his refuge, whither he had fled: and he shall abide in it to the death of the high priest, who was anointed with the holy oil.

26 But if the slayer shall at any time come without the border of the city of his refuge, whither he had fled;

27 And the avenger of blood find him without the borders of the city of his refuge, and the avenger of blood shall kill the slayer; he shall not be guilty of blood:

28 Because he should have remained in the city of his refuge until the death of the high priest: but after the death of the high priest the slayer shall return into the land of his possession.

29 So these [things] shall be for a statute of judgment to you throughout your generations in all your dwellings.

30 Whoever killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person [to cause him] to die.