What is this Pasuk coming to teach us?
Rashi #1: It teaches us not to render the land Tamei, 1 thereby forcing Hashem to dwell in the land when it is Tamei' - since Hashem's Shechinah rests in Yisrael even when they are Tamei.
Rashi #2 (in Yoma, 85a): It teaches us a. that murder is a terrible sin that contaminates the land and, and b. that if one contaminates the land, the Shechinah will not rest in it.
Ha'amek Davar: With reference to a Rotze'ach be'Shogeg, it teaches us that it renders the land Tamei 2 and that, as a result, Yisrael and the Shechinah are forced to go into exile. 3
RS"R Hirsh: If the nation is apathetic about murder, this is like denial of the Divinity of [the source of the Neshamah of] man, and proclaims that the land is Tamei. See also 35:34:1:2*.
Ha'amek Davar; Because, just Tum'ah applies whether it is be'Meizid or be'Shogeg, so too is murder Metamei the land, whether one killed be'Meizid or be'Shogeg.
See Ha'amek Davar.
