The Cities of Refuge in the Messianic Era

The Torah designates six cities of refuge to which a person who has inadvertently killed someone can flee and atone for his deed. When Moshiach comes and the borders of Israel are expanded, three more cities of refuge will be established. But why will additional cities be necessary in the Messianic Era? If peace will reign and violence will disappear from the face of the earth, what purpose will these cities of refuge serve? Although no new acts of violence will occur, the cities of refuge will allow those Jews who accidentally killed someone throughout the centuries of exile to seek atonement and be worthy of the Messianic Era. (The Rebbe, Rosh Chodesh Elul 5746)