Asylum Cities

Numbers 35:9-15 (MSG)
[9] GOD spoke to Moses: [10] "Speak to the People of Israel. Tell them, When you cross the River Jordan into the country of Canaan, [11] designate your asylum-cities, towns to which a person who accidentally kills someone can flee for asylum. [12] They will be places of refuge from the avenger so that the alleged murderer won't be killed until he can appear before the community in court. [13] Provide six asylum-cities. [14] Designate three of the towns to the east side of the Jordan, the other three in Canaan proper—asylum-cities [15] for the People of Israel, for the foreigner, and for any occasional visitors or guests—six asylum-cities to run to for anyone who accidentally kills another.

Numbers 35:26-27 (MSG)
But if the murderer leaves the asylum-city to which he has fled, and the avenger finds him outside the borders of his asylum-city, the avenger has a right to kill the murderer. And he's not considered guilty of murder.