Nazir, Chapter 1, Mishnah 7. This mishnah deals with a person who takes a nazirite vow using a number connected to the count of the days of the year, and with the question of how his vow is to be interpreted.
The text of the mishnah:
"Hareini nazir keminyan yemos hachamah" - one who takes this vow, "moneh nezirus keminyan yemos hachamah" - he counts nazirite terms according to the number of days in the solar year. That is, he must observe as many separate nazirite terms as there are days in the year: three hundred sixty five separate terms of nezirus, of thirty days each.
One should not mistakenly interpret this as a single nazirite term lasting three hundred sixty five days; his intention is three hundred sixty five distinct nazirite terms.
The testimony of Rabbi Yehudah:
The mishnah continues: "Amar Rabbi Yehudah: ma'aseh shehayah" - Rabbi Yehudah said: there was an actual incident. There was a man who took such a vow, and once he completed all the nazirite terms, he died. That man fulfilled three hundred sixty five separate nazirite terms, a period of over thirty years, exactly as the first tanna states in our mishnah.
The position of Rabbi in Mishnah 4:
The Gemara explains what Rabbi Yehudah came to prove. In Mishnah 4 the tannaim disagreed about a person who says that he is a nazir according to the number of hairs on his head:
The first tanna: these are separate nazirite terms.
Rabbi: this is nothing other than one long nazirite term for the rest of his life, since the hairs of his head are far more numerous than the number of months in his lifetime, and so he will be a nazir with one long nezirus for all his days.
How Rabbi Yehudah understood Rabbi's view:
Rabbi Yehudah understood that Rabbi disagrees in our mishnah as well, and that in his opinion one who says "Hareini nazir keminyan yemos hachamah" intends one of two possible meanings:
As long as the sun shines - that is, for all the days of his life.
Three hundred sixty five times three hundred sixty five days - a number of days that no person lives.
Rabbi Yehudah therefore came to refute this understanding, and he brought an incident that actually occurred: a man who in fact completed his vow and only afterward died. From here we see that fulfilling the vow is possible, and that it does not mean that the person remains a nazir his entire life as Rabbi holds, but rather three hundred sixty five separate nazirite terms, which can be fulfilled during a person's lifetime over a period of more than thirty years.
In summary: in this mishnah we learned that one who says "Hareini nazir keminyan yemos hachamah" counts three hundred sixty five separate nazirite terms of thirty days each, and not one long nezirus. Rabbi Yehudah, who understood that according to Rabbi the one who vows intends a single nezirus for all the days of his life, brought an incident that occurred with a man who completed all his nazirite terms and afterward died - proof that the vow can indeed be fulfilled, in accordance with the view of the first tanna.