Why does the Torah insert Birchas Kohanim immediately after the Parshah of Nazir?
Moshav Zekenim (on Pasuk 11) #1 and Ba'al ha'Turim (on Pasuk 21): It is a hint that a Kohen who drank wine is not permitted to Duchen. 1 And we learn from here that a Kohen who is Shikor is forbidden to Duchen.
Moshav Zekenim (in Pasuk 11) #2: Because the Kedushah of a Nazir is like that of a Kohen Gadol - like whom he may not render himself Tamei even for relatives
However, as opposed to a Nazir - a Kohen who ate grape-pits is permitted. "Lesharso u'Levarech bi'Shmo" (Devarim 10:8) - a Kohen who serves is permitted Chartzan and forbidden wine, also one who blesses. One might have thought that just like a Kohen Ba'al-Mum may not serve, he may not Duchen - However, the Hekesh to Nazir refutes this. Moshav Zekenim: Megilah, 24b forbids a Kohen with Mumim on his hands to Duchen, for people look at him! The Tosefta says that this is only Mumim on his hands and face, but other Mumim do not disqualify him. Even on his hands and face, he is permitted in his city, since people are used to him and will not look at him. See also Torah Temimah, note 130, who elaborates.
