Tosafot and Rambam disagree what is the meaning of our Mishna TB Nazir 39

The first five chapters of our massekhet deal with the topic how does one become a nazir. The sixth chapter deals with the three prohibitions the nazir must observe, abstaining from wine and all grape products, not cutting the hair, and not becoming ritually unready contacting a dead body. The first five dappim discussed all the issues surrounding the prohibition of abstaining from wine in all great products. The Mishnah on today’s daf TB Nazir 39 changes topic and moves on to the prohibition of getting a haircut during the period of one’s nazirut.

MISHNA: “A naziriteship of unspecified length lasts for thirty days. If a nazirite shaved his hair during that period, or if he was shaved by bandits [listim] against his will, this negates thirty days of his naziriteship (סוֹתֵר שְׁלֹשִׁים יוֹם)” (Sefaria.org translation) At the end of the person’s nazirut, he must have a significant amount of hair based on Number 6:5 “Throughout the term of their vow as nazirite, no razor shall touch their head; it shall remain consecrated until the completion of their term as nazirite of YHVH, the hair of their head being left to grow untrimmed (גַּדֵּ֥ל פֶּ֖רַע שְׂעַ֥ר רֹאשֽׁוֹ).” The rabbis determine that a person needs a minimum of 30 days to have a significant amount of nazirite hair growth.

Tosafot and Rambam disagree what is the meaning of “negates thirty days of his naziriteship (סוֹתֵר שְׁלֹשִׁים יוֹם).” This disagreement has a practical outcome for the nazir.

Tosafot ד"ה סְתַם נְזִירוּת  שְׁלֹשִׁים יוֹם explains that this haircut does not interrupt the person’s count of days he vowed to be a nazir. Nevertheless, he still needs a minimum of 30 days of hair growth. For example, a person who vowed to be a nazir for 30 days, but got a haircut on the 20^th day, he only needs 10 more days to fulfill the number of days of its vow. Before he can bring his three sacrifices, he must add another 20 days of hair growth so he can reach the minimum requirement of 30 days of hair growth.

Rambam understands “negates 30 days” to mean that the nazir’s count of days is interrupted until he has 30 days’ worth of hair growth. For example, a person who vowed to be a nazir for 30 days, but got a haircut on the 20^th day, his nazirut is interrupted. He must wait 30 days so his hair length will meet the minimum requirement. After those 30 days, the nazir resumes his count and adds the last 10 days to fulfill his vow.

“When a nazirite drinks wine or eats a grape product, even if he does so for many days, he does not invalidate even one of the days of his nazirite vow. Similar [principles apply] if he shaved a minority of his head, whether intentionally or unintentionally. If, however, the majority of his head was shaved, whether with a razor or through another means which is as effective as a razor and enough of the hairs to fold over their head to their base were removed whether intentionally or unintentionally - even if thieves shaved his head against his will - thirty days are invalidated. [He must wait] until he has an uncut mane of hair. Afterwards, he counts [the remaining days].

“What is implied? A person took a nazirite vow for 100 days and after 20 days, the majority of his hair was shaved. He must wait 30 days until the hair of his head grows. After 30 days, he counts eighty days to complete his nazirite vow. Throughout these 30 days, he must observe all the particular nazirite law, but the days are not counted [as part of his nazirite vow].” Rambam, Mishneh Torah, Hilkhot Nazir 6:1-2