Deuteronomy 19:6-8 Good News Bible Anglicised (GNBDC)

6. If there were only one city, the distance to it might be too great, and the relative who is responsible for taking revenge for the killing might catch him and in his anger kill an innocent neighbour. After all, it was by accident that he killed his neighbour who was not his enemy.

7. This is why I order you to set aside three cities.

8. “When the Lord your God enlarges your territory, as he told your ancestors he would, and gives you all the land he has promised,

Deuteronomy 19