Numbers 35:6,7

Cities for refuge Or, of escape for manslayers. And these cities are assigned among the Levites, partly because they might be presumed to be the most proper and impartial judges between manslayers and wilful murderers; partly because their presence and authority would more effectually bridle the passions of the avenger of blood who might pursue him thither; and perhaps to signify that it is only in Christ (whom the Levitical priests represented) that sinners find refuge and safety from the destroyer. Three of these cities of refuge were in the land of Canaan, and three on the other side Jordan, (Numbers 35:14,) and the names of them are set down, Joshua 20:7. Of the forty-eight cities given to the Levites, thirteen were appointed for the priests.