2,913. A Nazir and Meis Mitzvah
Hilchos Nezirus 7:12
Becoming unclean through corpse impurity for purposes of a mitzvah means that the nazir was walking on the road and he came across a corpse with no one else around to bury it. In such a case, he should allow himself to be rendered unclean through corpse impurity and bury the deceased. This law was transmitted via our oral tradition.
Hilchos Nezirus 7:13
If a nazir and a kohein find a corpse that is a mitzvah to bury, the nazir should allow himself to be rendered unclean even though it means that the days he already observed will be voided and he will have to bring the impurity offerings; the kohein should not allow himself to be rendered unclean. This is because the nazir’s holiness is of a temporary nature, even if he committed to be a nazir forever, while the kohein’s holiness is of an eternal nature.