Numbers 35:14

Three cities, etc. Although there were, in the land of Canaan, nine tribes, and here only two and one half, the number of their cities of refuge was the same. Because Gil’ad was rife with murderers, as it is written, “Gil’ad, city of evildoers, bloody ambush.”

three you shall appoint beyond Jordan, and three in the land of Kenaan; cities of refuge shall they be.

YE SHALL GIVE THREE CITIES BEYOND THE JORDAN. “And even though in the land of Canaan there were nine tribes, and here [on the east side of the Jordan] there were only two [and a half], Scripture gave them an equal number of cities of refuge, because in Gilead [on the east side of the Jordan] murderers were numerous, as it is written, Gilead is a city of wrong-doers; it is covered with footprints of blood.” This is Rashi’s language, based on the words of our Rabbis. Now even though the [cities of] refuge were only for those who killed in error [and these murderers of Gilead killed deliberately], they would kill in treachery and make themselves appear as if they had done it in error, and therefore it was necessary to increase [proportionately] the number of their cities of refuge, in order to be able to take in all of them, since one could not tell who had killed deliberately. If so, [we must say that] the Holy One, blessed be He, commanded this on account of the future [since He knew that murderers in Gilead would be numerous], similar to that which it says [of the future generations], and this people will rise up, and go astray. Or perhaps the Rabbis will say that the climate of the land of Gilead was conducive to producing murderers since it became a nation.
But I wonder! For in the opinion of our Rabbis, of blessed memory, the [cities mentioned in the] verse which says, and beside them [i.e., apart from the six cities of refuge], ye shall give [to the Levites] forty and two cities, were all commanded as cities of refuge, and thus there were thirty-six of them in the land of Canaan, and six beyond the Jordan, which, as clearly stated in Joshua Chapter 21 (see Note 68), were in the land of Canaan, we must now deduct the three main cities of refuge, leaving us a total of thirty-five additional cities of the Levites in the land of Canaan – and consequently a total of seven such additional cities for beyond the Jordan to complete the total of forty-two — we must perforce understand Ramban’s language in speaking of thirty-six cities for the land of Canaan and six for beyond the Jordan as based on the theory mentioned above in the text that the factor of appraised value was also taken into consideration, and hence the seven cities on the eastern side of the Jordan were regarded as six, thus leaving a total of thirty-six for the land of Canaan. and they all offered protection, in the opinion …

את שלש הערים תתנו מעבר לירדן, the ones Moses had already set aside for this purpose as we know from Deuteronomy 4,41.

את שלש הערים וגו'...מעבר לירדן ואת שלש הערים וג' בארץ כנען “the three towns etc.; and the three towns etc.; in the land of Canaan.” The Talmud tractate Makkot folio 9 raises the question why it was that both on the west bank of the Jordan and on the east bank three towns of refuge for potential inadvertent killers were provided when more than 80% of the population resided on the west bank of the Jordan? The answer given by the scholar Abbaye is that the area known as Gilead on the east bank was known to harbour many murderers. He based himself on what is written in the Book of Hoseah 6,8: גלעד קרית פועלי און עקובה מדם, “Gilead is a city of evildoers, tracked up with blood.” Rabbi Elazar there adds that the word עקובה used by the prophet means that people lay in wait, and ambushed those whom they planned to kill. How do these statements answer our question seeing that the cities of refuge were not provided for intentional murders? The prophet accused the people Gilead of committing deliberate murders! The answer is that the fact that seeing that unintentional killings were common place in Gilead, this encouraged intentional killers to pretend that they had committed unintentional killing. G–d arranged for unintentional killers to be residents of that area in order to be able to tell between deliberate murders committed in the absence of witnesses, and unintentionally committed killings. Their victims would be the ones who had previously committed intentional killings but could not be brought to court due to absence of witnesses. The Talmud on the folio next to the one we quoted uses Samuel I 24,14: מרשעים יצא רשע, “wicked deeds have a habit of being performed by wicked people.” [a quote from David who after having cut off a piece of King’s Shaul’s cloak instead of killing him as his pursuer, wanted to convince him that the people who had accuse him as being his enemy had evil intentions. Ed.] If one person had killed unintentionally, without there being any witnesses, so that he did not bother to go to a city of refuge, G–d arranges that he will do something similar with witnesses, but the victim having previously guilty of intentional undetected murder.