Deuteronomy 19:7-10 NIV

7 This is why I command you to set aside for yourselves three cities.
8 If the LORD your God enlarges your territory, as he promised on oath to your ancestors, and gives you the whole land he promised them,

References for Deuteronomy 19:8

9 because you carefully follow all these laws I command you today—to love the LORD your God and to walk always in obedience to him—then you are to set aside three more cities.

References for Deuteronomy 19:9

10 Do this so that innocent blood will not be shed in your land, which the LORD your God is giving you as your inheritance, and so that you will not be guilty of bloodshed.

References for Deuteronomy 19:10