Deuteronomy 19:8-10

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

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

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