Why does the Torah refer to six plus forty-two Arei Miklat? Why does it not simply refer to forty-eight Arei Miklat?
Makos, 10a, 13a: Because there are two distinctions between the two sets of Arei Miklat: 1. Whereas the six initial towns are Kolet (protect a murderer against the Go'el ha'Dam, and forbid him to leave before the Kohen Gadol dies) irrespective of whether he is aware that he entered an Ir Miklat or not, the forty-two additional ones are Kolet only if he knows that it is an Ir Miklat. 2. Whereas a murderer in one of the six initial Arei Miklat is exempt from paying the Levi'im rental for his apartment, in one of the forty-two, he is obligated to pay.
Why does it say "ve'Zeh Devar ha'Rotze'ach"?
Hadar Zekenim; Da'as Zekenim and Rosh (both in Devarim 15:2, from Makos 2:8): If a murderer was exiled to an Ir Miklat, and the residents wanted to honor him, he must say 'I am a murderer.' If they say 'even so', he may accept from them. "V'Zeh Devar"