We know that the Kohanim are from the tribe of Levi. Why does the Torah need to mention it?
Gitin, 59b: To teach us that Kohanim take precedence over Levi'im in all matters. 1
Sifri: To incorporate Kohanim who are Ba'alei-Mumin in the Din of Eglah Arufah. 2
What is the significance of all the details listed in the Pasuk?
Kol Eliyahu: They comprise the five issues that comprise the Kehunah: 1. "Lesharso" - the Avodah; 2. "Levarech be'Shem Hashem" - Birkas Kohanim; 3. "Al Pihem Yih'yeh" - the Eglah Arufah; 4. "Kol Riv" - giving a Sotah to drink (in connection with a quarrel between husband and wife); 5. "Kol Nega" - the Taharah of a Metzora (to declare him a Musgar or a Muchlat - Targum Yonasan).
Why are the Kohanim designated to officiate at the ceremony of the Eglah Arufah"?
Seforno: a. Because they are the ones who serve in the Beis-Hamikdash and who are therefore eligible to atone for the innocent blood that was shed, and b. Because, in their capacity as Dayanim and consultants regarding Nega'im, they are conversant with human nature, in which case they may well be able to identify the person who has sullied himself with the sin of murder.
Oznayim la'Torah: Because following the Arifah, which corresponds to the Shechitah of a Korban - which a Zar is eligible to perform,"Kaper le'Amcha Yisrael" corresponds to the Zerikas ha'Dam, which requires Kehunah. 1
And as Rashi explains, the Kohanim were the ones to say "Kaper le'Amcha Yisrael".
"Le'sharso u'Le'varech". What is the significance of the comparison of B'rachah to Sheirus?
Yerushalmi Ta'anis, 4:1: To teach us that Birchas Kohanim, like Sheirus, must be performed standing. 1
See Torah Temimah, note 42.
"Kol Riv ve'Chol Nega". What is the significance of the comparison of Rivim to Nega'im?
Sanhedrin, 34b: To teach us that a. like Nega'im, Rivim (Dinei Mamonos) must be judged in day-time 1 and b. that they may not be judged by Dayanim who are blind (in both eyes). 2
Yerushalmi Nedarim, 9:1: To teach us that, just as Nega'im can only be inpected if the Kohen's eyes are not dimmed ("le'CHol Mar'eh Einei ha'Kohen", so too, can a Dayan whos eyes are dimmed, not judge Dinei Mamonos.
