The Gemara answers: Bar Padda could have said to you: Say the latter clause of that mishna: Rabbi Eliezer says: It negates only seven days. If it enters your mind that we require thirty days for a term of naziriteship, the nazirite should negate all of them, since he is still in the middle of his naziriteship. This proves that an unspecified naziriteship is only twenty-nine days long.

The Gemara responds that Rav Mattana can explain Rabbi Eliezer’s opinion as follows: This does not prove that an unspecified term of naziriteship is less than thirty days, as Rabbi Eliezer holds that the legal status of part of the day is like that of an entire day, and it is viewed as though the nazirite has completed his term of naziriteship at the start of the thirtieth day.

The Gemara raises a difficulty with Rabbi Eliezer’s opinion. We learned in the mishna (16a): If one says: I am hereby a nazirite for one hundred days, if he became impure on the one hundredth day, it negates the entire tally. He must bring offerings for having become impure, and he then begins his term of naziriteship anew. Rabbi Eliezer says: It negates only thirty days. The Gemara comments: And if it enters your mind that Rabbi Eliezer holds that the legal status of part of the day is like that of an entire day, the nazirite should negate seven days because it is considered as though he became impure after completing his term of naziriteship. And if he does not hold that part of the day is like an entire day, he should negate all of the days, since he became impure during his naziriteship.

The Gemara answers: Actually, we do not say that the legal status of part of the day is like that of an entire day. The Gemara asks: If that is so, then let him negate all of the days. Reish Lakish said that this is the reason of Rabbi Eliezer: The verse states: “This is the law of the nazirite, on the day when the days of his consecration are complete” (Numbers 6:13). The Torah stated: If he became impure on the day of the completion of his term of naziriteship, give him the halakha of an unspecified nazirite, and he must recount an unspecified term of naziriteship, which is thirty days.

§ Until this point the Gemara has been attempting to prove whether the halakha is in accordance with the opinion of Rav Mattana or bar Padda. The Gemara now suggests: Let us say that this is parallel to a dispute between tanna’im, as it is taught in a baraita: The verse states: “Until the days are complete, in which he consecrated himself to the Lord, he shall be holy, he shall let the locks of the hair of his head grow long” (Numbers 6:5).

I hear from this: The least amount of days that the plural “days” can indicate is two, implying that one can become a nazirite for a term of two days. Therefore, the verse states: “He shall be holy, he shall let the locks of the hair of his head grow long,” and there is no significant growth of hair in less than thirty days. This is the statement of Rabbi Yoshiya.

Rabbi Yonatan says: This proof is not needed, as the verse says: “Until the days are complete.” What are the days that require completion? You must say this is referring to the days of a month. Since a lunar cycle lasts for approximately twenty-nine and a half days, some months are twenty-nine days, whereas full months are thirty days. This demonstrates that a term of naziriteship must be at least one month.

The Gemara suggests: What, is it not the case that Rav Mattana said in accordance with the opinion of Rabbi Yoshiya, who derives the minimum length of a term of naziriteship from the phrase “he shall be holy, he shall let his hair grow long,” and therefore a term of naziriteship lasts thirty days, and bar Padda said in accordance with the opinion of Rabbi Yonatan, who derives this halakha from the length of a month, and since a month can be twenty-nine days, the minimum length of a term of naziriteship is also twenty-nine days?

The Gemara responds: Rav Mattana could have said to you: Everyone agrees that we require a term of naziriteship to last at least thirty days, and here they disagree with regard to whether “until” means until and including. Rabbi Yoshiya holds that “until the days are complete” indicates that a term of naziriteship must last until, but not necessarily including, the thirtieth day of a full month. Consequently, he derives the minimum length of a term of naziriteship from the phrase “he shall let the locks of the hair of his head grow long.” And Rabbi Yonatan holds that the term “until” means until and including the thirtieth day of a full month, and he derives the minimum length of a term of naziriteship from the phrase “until the days are complete.”

The Gemara now analyzes the baraita that cites the opinions of Rabbi Yoshiya and Rabbi Yonatan. The Master, Rabbi Yonatan, said: What are the days that require completion? You must say this is referring to the thirty days of a full month. The Gemara asks: But say it is referring to the seven days of a week. The Gemara responds: In the case of a week, is there ever a week that is lacking? All weeks are seven days. Conversely, since some months are twenty-nine days and others are thirty days, it can be said that the thirtieth day completes that which was lacking.