Deuteronomy 19:8-10

8And if the LORD thy God shall enlarge thy land, as he hath sworn to thy fathers, and give thee all the land which he promised to give to thy fathers;

9If thou shalt keep all these commandments to do them, which I command thee this day, to love the LORD thy God, and to walk ever in his ways; then shalt thou add three cities more for thee, besides these three:

10That innocent blood may not be shed in thy land, which the LORD thy God giveth thee for an inheritance, and so blood be upon thee.