Deuteronomy 19:9-13

if you carefully follow all of this commandment which I am commanding you today, to love the Lord your God, and to walk in His ways always—then you shall add three more cities for yourself, besides these three.

So innocent blood will not be shed in the midst of your land which the Lord your God is giving you as an inheritance, and guilt for bloodshed will not be on you.

“But if there is a person who hates his neighbor, and waits in ambush for him and rises up against him and strikes him so that he dies, and he flees to one of these cities,

then the elders of his city shall send men and take him from there, and hand him over to the avenger of blood, so that he may die.

You shall not pity him, but you shall eliminate the guilt for the bloodshed of the innocent from Israel, so that it may go well for you. Laws of Landmark and Testimony