Why does the Torah insert details concerning the Arei Miklat here? What is the significance of the sequence of the current Parshiyos?
Seforno: Having taught the Dinim concerning the Shoftim, the king, the Kohanim and the Nevi'im, the Torah deals with the Mitzvos that are incumbent upon the Shoftim - designating the Arei Miklat, delineating the borders of Eretz Yisrael, cross-examining witnesses and accepting them. 1
Seforno: Followed by the Mitzvos that are incumbent upon the king - going to war, 20:1-9; approaching a town, 20:10-28 and laying siege to a town, 20:19- 20, and followed by the Mitzvos that are incumbent upon both the Kohanim and the Shoftim - the Parshah of Eglah Arufah. 21:1-9.
What is the definition of "Arim"?
Sifri: Refer to Bamidbar, 35:11:2:1 and Torah Temimah there, note 12.
Why does the Torah insert the (otherwise superfluous) word "Shalosh Arim Tavdil Lach"?
Sifri: To preclude a Nochri, who is Chayav Misah by the sword, even if he kills be'Shogeg. 1
See Torah Temimah, note 2.
What is "be'Soch Artz'cha" coming to prelude?
Sifri: It precludes border towns (with neighboring nations) from becoming Arei Miklat.