Nazir 56B

מה ימי חלוטו טעון תגלחת ⁠— אף ימי ספרו. ומה ימי חלוטו אין עולין לו מן המנין ⁠— אף ימי ספרו.

Just as the days of his confirmed tzara'at require shaving, so too, the days of his counting require shaving; and just as the days of his confirmed tzara'at do not count as part of his tally of naziriteship, so too, the days of his counting should not count toward his term of naziriteship?

יכול אף ימי הסגרו כן? והדין נותן: חלוט מטמא משכב ומושב, וימי הסגרו מטמא משכב ומושב. אם למדת לימי חלוטו שאין עולין לו מן המנין ⁠— אף ימי הסגרו אין עולין לו מן המנין.

One might have thought that even his days of quarantine as a metzora should share the same halakha and not be counted. And it is logical that those days should not count for him either, as the two states are comparable: A confirmed metzora renders items ritually impure through lying or sitting, and a metzora in the days of his quarantine also renders items impure through lying or sitting. Consequently, if you learned with regard to the days of confirmed tzara'at that they do not count as part of his tally, so too, the days of quarantine should not count as part of his tally either.

אמרת: לא, אם אמרת בימי חלוטו, שכן חלוטו טעון תגלחת ומביא קרבן, לפיכך אין עולין. תאמר בימי הסגרו, שאין טעון תגלחת, ואינו מביא קרבן, לפיכך יעלו למנין.

The Talmud rejects this argument: You can say in response: No, if you said this halakha with regard to the days of confirmed tzara'at, the reason is that his confirmed state of tzara'at requires him to shave after he is healed and to bring an offering before he can commence his naziriteship. Therefore, these days do not count toward his naziriteship. However, will you say the same with regard to the days of his quarantine, which do not require shaving and for which he does not bring an offering? Therefore, perhaps they should count toward his tally.