The גמרא asks what the halacha would be if someone said he is like “משה רבינו on the seventh day of אדר”. Is the person referring to the day משה רבינו died and he means to take on נזירות because lots of people took on נזירות the day משה רבינו died because of their pain, or do we say that he is משה רבינו on the day he was born in which case he is just taking on "שמחה"? תוספות in ד"ה כמשה asks how could those people who took on נזירות have ever gotten out of their נזירות? After משה רבינו died they went into ארץ ישראל and they couldn’t bring קרבנות חובה like the קרבנות נזיר since קרבנות like that could not be brought on a במה (based on the גמרא in זבחים דף קי"ח)? So if they couldn’t bring their קרבן נזירות how did they stop being a נזיר? He does not answer the question. Many מפרשים ask on תוספות that כלל ישראל didn’t move for 30 days after משה רבינו died and only moved into ארץ ישראל on the tenth of ניסן. If so, there are more than 30 days where the people could have been a נזיר and brought their קרבנות in the משכן. So why does תוספות say that they couldn’t have ended their נזירות? The אמבוהא דספרי in פּרשת נשא, אות פּ"ד has a beautiful answer. He says that the גמרא in פּסחים says that when a נשיא dies, everyone is supposed to be מטמא to him. If so, they would all be טמא מת and would need to wait seven days before they could start keeping their נזירות. At that time, thirty days later would have been after י׳ ניסן and they wouldn’t have been able to bring their קרבן.

If a person says he will be a נזיר when he has a child and also a נזיר now, then he starts keeping the second נזירות (נזירות שלו) now and then when he has a kid interrupts that נזירות and begins נזירות דבנו and then subsequently finishes whatever was leftover from נזירות שלו. If he becomes טמא during נזירות דבנו, ר׳ יוחנן says he is סותר everything until that point since his own נזירות and the נזירות of his son are one נזירות. The גמרא doesn’t discuss what would happen if he became טמא during the last portion where he is finishing off נזירות שלו. תוספות in ד"ה חדא says that it would certainly only beסותר נזירות שלו and not נזירות בנו since נזירות בנו has completed. However, would it be סותר just the last portion if נזירות שלו or the whole 30 days of נזירות שלו? The רמב"ם in הלכות נזירות פּרק ד׳ הל׳ ג says that it would only be סותר the most recent portion and the ראב"ד sats it would be סותר the whole 30 days of נזירות שלו. לכאורה the ראב"ד is correct. How could you become טמא and only be סותר half a נזירות? In מרן רי"ז הלוי in הלכות נזירות דף כ"א, the Brisker Rov z”l says that the רמב"ם takes the words of the גמרא of “כולה חדא נזירות” literally, that even though they are two קיומים of נזירות mixed together, they become one חפצא of נזירות. Therefore, once that is completed, the last days remaining from נזירות שלו become a separate חפצא of נזירות and would only affect themselves and not the earlier part of נזירות שלו, even though it is the same קיום. The ראב"ד learned the words כולה חדא נזירות to just mean that נזירות בנו is in the middle of נזירות שלו so it can affect it.