Deuteronomy 19:8-10

8“If the Lord your God 1enlarges your territory, just as He has sworn to your fathers, and gives you all the land which He 2promised to give your fathers-- 9if you 3carefully observe all this commandment which I command you today, 4to love the Lord your God, and to walk in His ways always--5then you shall add three more cities for yourself, besides these three. 10So innocent blood will not be shed in the midst of your land which the Lord your God gives you as an inheritance, and 6bloodguiltiness be on you.