DEU 19:8

8 “If you do everything that I am today commanding you to do, and if you love Yahweh our God, and if you conduct your lives as he wants you to do, Yahweh our God will give you much more land than you will have when you first occupy it, which is what he promised to do. He will give you all the land which he promised your ancestors that he would give to you. When he gives you that land, you must select three more cities [to which people may escape].