שלש ערים תבדיל לך בתוך ארצך, "Three cities you shall set aside for yourself in the midst of your land;" together with the three towns which Moses had already designated as cities of refuge on the east bank of the Jordan as reported in Deut. 4,41-43, this makes a total of 6 such cities. It is essential that these cities are regular, populated cities with all the normal amenities of a city, seeing the Torah wrote in verse 3 תכין לך הדרך, "prepare the way for yourself," and the Talmud Makkot 10 understands these words to mean that signs with the word מקלט, "refuge," must be posted on all the roads leading to such cities. This is in order for the unintentional killer not to lose time while trying to escape the vengeance of the slain man's family. On Psalms 25,8: "Good and upright is the Lord; therefore He shows the sinners the way," the sages say that these signs are designed to help unintentional sinners seeing their sin was inadvertent. We have another verse along similar lines in Job 36,22: "See, God is beyond reach in power; Who governs like Him?" The author refers to the unique attribute of God who helps the inadvertent sinner to rehabilitate himself.
The reason why the Torah continues with: "you shall divide your territory into three parts is that the cities of refuge should be situated so that their location effectively divides the land into three parts which are equi-distant from one another.
We should appreciate that the total number of 6 such cities reflects the principle of the 6 extremities of terrestrial earth (six directions) which we discussed already repeatedly. The first three cities which Moses set apart for this purpose on the east bank of the Jordan were quite unable to fulfill their function until they had been joined by these additional three cities on the west bank of which the Torah speaks here and which are as yet unnamed. There is a mystical element connected to this number 6 which also symbolizes 6 extremities in the celestial regions of the universe in which the soul of the sinner will have to receive his pardon from the loving kindness extended to it by Hashem.
Although the three cities which Moses had already set aside were by themselves incapable of performing their function until there were six such cities, when Moses designated them as such he had in mind that they should represent the three letters in the tetragrammaton י-ה-ו. We find that seven letters in the aleph bet are described in the Sefer Yetzirah as כפולות, as having a dual function. In chapter 4, Mishnah 12, of that book we read: "whereas with two stones one can only build two houses, with three stones (read letters) one can build six houses, whereas with four stones one can build 24 houses." [Although I do not profess to understand the deeper meaning of these progressions, or צירופים, permutations, as they are called in kabbalistic terms, it is clear that our author means that the three original cities set aside by Moses enabled the other three cities to become operational when they would be established and as such perform a dual function also. Mishnah 13 in Sefer Yetzirah chapter one, deals with the permutations of the three letters of the tetragrammaton. Ed.] It appears that whereas three cities are intended as a refuge for the body, the other three complement the whole function by being a refuge for the soul. In terms of what happens to the person who killed unintentionally when he arrives in the hereafter then, it is essential that at the time when he was in a city of refuge on earth there had been 6 such cities (although the killer can only live in one of them.) [I am omitting the balance of this paragraph (6 lines) as I do not understand it. It describes the progression of the souls in the hereafter from one part of "Gan Eden" to another. Ed.] The words תכין לך הדרך, are perceived as a preparation for such killers to escape this world for the world to come.