Numbers 35:27

and the avenger of blood should find him without the bounds of the city of his refuge, and the avenger of blood should kill the slayer, he is not guilty.

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

and the avenger of blood finds him outside of the border of his city of refuge, and the avenger of blood kills the man slayer, he shall not be guilty of blood,