Deuteronomy 19:1-3

When the Lord thy God hath destroyed the nations, whose land he will deliver to thee, and thou shalt possess it, and shalt dwell in the cities and houses thereof:

Thou shalt separate to thee three cities in the midst of the land, which the Lord will give thee in possession,

Paving diligently the way: and thou shalt divide the whole province of thy land equally into three parts: that he who is forced to flee for manslaughter, may have near at hand whither to escape.