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
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.
Kol Eliyahu: Because the Pasuk lists 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; 1 ; 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). 2
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 reqquires Kehunah.
The Tum'ah of a Metzora is also perfomed by the Kohanim! Perhaps the G'ra did not include Tum'as Metzora because if the Kohen declares Tahor a person who is Tamei, he is not Tahor (Rashi Vayikra 13:37. However, refer to Vayikra 13:37:154:13-3 and the note there
What is the significance of the comparison of B'rachah to Sheirus (See 2:5:1:2)?
Yerushalmi Ta'anis, 4:1: To teach us that Birchas Kohanim, like Sheirus, must be performed standing. 1
See Torah Temimah, note 42.
What is the significance of the comparison of Rivim' to Nega'im (See 2:5:1:2)?
