משנה אויף במדבר 10:11

A high priest and a nazirite may not defile themselves with their [dead] relatives, but they may defile themselves with a neglected corpse. If they were walking on the path and found a neglected corpse: Rabbi Eliezer says: the high priest should defile himself but not the nazirite. But the Sages say: the nazirite should defile himself but not the high priest. Rabbi Eliezer said to them: the priest should defile himself, for he does not offer a sacrifice for his defilement, and the nazirite should not defile himself, for he does offer a sacrifice on defilement. They said to him: the nazirite should defile himself, for his holiness is not permanent, and the priest should not defile himself, for his holiness is permanent.