2,912. When a Nazir Should Violate

Hilchos Nezirus 7:10

It goes without saying that if a nazir is rendered unclean by some other kind of impurity, then the days of his impurity count towards his nezirus and none of the days that he already observed are voided. If he’s rendered unclean through corpse impurity while he has tzaraas, then all of his completed days are voided. This is because he’s still a nazir despite his impurity.

Hilchos Nezirus 7:11

A nazir is permitted to render himself unclean through corpse impurity for purposes of a mitzvah, and he may shave for a mitzvah,* but he may not have any wine, neither for a mitzvah nor for voluntary reasons. Accordingly, if someone made an oath to drink wine that day, it’s a mitzvah for him to drink. If he then makes a nazirite vow, the nezirus takes effect and “outranks” his oath, with the result that he’s prohibited to drink wine. It should go without saying that a nazir may not drink the wine of kiddush or Havdalah, which is only an obligation under rabbinic law.

*When is it a mitzvah to shave? See halacha 7:15.