70 Nazir 6/5-7

(5) Three categories are prohibited for a nazir: impurity, shaving, and grape products. The stringency with impurity and shaving over grape products is that impurity and shaving void [his vow] and grape products do not void. The stringency with grape products over impurity and shaving is that grape products are not permitted by implication (there are no cases which allow permission to violate the restriction because of other Torah commandments), while impurity and shaving are permitted by implication: in shaving for a commandment and for an unclaimed dead body. The stringency with impurity over shaving is that impurity voids all [of his vow] and one is obligated for a sacrifice on its account, and shaving only voids thirty days [of his vow], and one is not obligated for a sacrifice on its account.

(6) How does shaving for impurity [work]? "He would be sprinkled on the third and the seventh [days], he would shave on the seventh, and bring his sacrifice on the eighth. If he shaved on the eighth, he would bring his sacrifice on that day," according to the words of Rabbi Akiva. Rabbi Tarfon said to him: "What is the difference between this and a case of leprosy?" He said to him: "This one's purity is dependent on his days, [while] the leper's purity is dependent on his shaving, and he does not bring a sacrifice until the sun sets."

(7) How does shaving for purity [work]? "He would bring three animals: a sin-offering, a burnt-offering, and a peace-offering. Then he slaughters the peace-offering and shaves after it," according to the words of Rabbi Yehuda. Rabbi Elazar says: "He would only shave after the sin-offering, as the sin-offering comes first in every instance." If he shaved after one of the three, he fulfilled his obligation.