Jamieson, Fausset and Brown on Deuteronomy 19:2

CHAPTER 19

De 19:1-13. Of the Cities of Refuge.

2. Thou shalt separate three cities for thee in the midst of thy land--Goelism, or the duty of the nearest kinsmen to avenge the death of a slaughtered relative, being the customary law of that age (as it still is among the Arabs and other people of the East), Moses incorporated it in an improved form with his legislative code. For the protection of the unintentional homicide, he provided certain cities of refuge--three had been destined for this purpose on the east of Jordan (De 4:41; Nu 35:11); three were to be invested with the same privilege on the west of that river when Canaan should be conquered.

in the midst of thy land--in such a position that they would be conspicuous and accessible, and equidistant from the extremities of the land and from each other.