Deuteronomy 19:3-4

19:3 You shall build a roadway and divide into thirds the whole extent of your land that the Lord your God is providing as your inheritance; anyone who kills another person should flee to the closest of these cities. 19:4 Now this is the law pertaining to one who flees there in order to live, if he has accidentally killed another without hating him at the time of the accident.

Deuteronomy 19:6

19:6 Otherwise the blood avenger will chase after the killer in the heat of his anger, eventually overtake him, and kill him, though this is not a capital case since he did not hate him at the time of the accident.