Deuteronomy 19:2-9

2you are to set apart three cities for yourselves within the land the Lord your God is giving you to possess.

3You are to determine the distances and divide the land the Lord your God is granting you as an inheritance into three regions, so that anyone who commits manslaughter can flee to these cities.

4“Here is the law concerning a case of someone who kills a person and flees there to save his life, having killed his neighbor accidentally without previously hating him:

5If, for example, he goes into the forest with his neighbor to cut timber, and his hand swings the ax to chop down a tree, but the blade flies off the handle and strikes his neighbor so that he dies, that person may flee to one of these cities and live.

6Otherwise, the avenger of blood in the heat of his anger might pursue the one who committed manslaughter, overtake him because the distance is great, and strike him dead. Yet he did not deserve to die, since he did not previously hate his neighbor.

7This is why I am commanding you to set apart three cities for yourselves.

8If the Lord your God enlarges your territory as he swore to your ancestors, and gives you all the land he promised to give them —

9provided you keep every one of these commands I am giving you today and follow them, loving the Lord your God and walking in his ways at all times — you are to add three more cities to these three.