What sin is the Nazir guilty of?
Rashi: He is guilty of not having been careful not to become Tamei.
Rashi #2 (citing R. Elazar ha'Kapar): He is guilty of desisting from wine. 1
What does the Torah mean when it writes "v'Kidash Es Rosho"?
Rashi: The Pasuk means that he is obligated to begin the Nezirus all over again.
From where must the Nazir begin counting?
Rashi: From the beginning, as the following Pasuk clearly indicates.
QUESTIONS ON RASHI
Rashi writes that R. Elazar ha'Kapar holds that his sin was desisting from wine. If so, even a Nazir Tahor should bring this Korban!
Moshav Zekeinim: If he did not become Tamei, the Mitzvah overrides the Aveirah. If he became Tamei, the first days are lost, and there is only the Aveirah.