Deuteronomy 19:8-10

And if the LORD 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; If 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, beside these three: That innocent blood be not shed in thy land, which the LORD thy God giveth thee {for} an inheritance, and {so} blood be upon thee.