Abaye said to him: If so, the Sages should likewise decree in the case of one who takes a vow for one day that he must keep the vow until nightfall of the following day, due to the confusion that might be caused in a case where one said that his vow applies today. If the vow expires in the middle of the day, twenty-four hours after he took the vow, people might think that if one takes a vow in the morning and applies it to this day, it also expires in the middle of the day.

Rav Yosef said to him: A vow taken for this day might be interchanged with a vow taken for one day, and one might erroneously conclude that a vow taken for one day expires at nightfall. However, a vow taken for one day is not interchanged with a vow taken for today, and there is no concern that one who takes a vow for today will erroneously conclude that it expires in the middle of the day.

Ravina said: Mareimar said to me: Your father said as follows, in the name of Rav Yosef: In accordance with whose opinion is this halakha taught by Rav Yirmeya bar Abba? It is in accordance with the opinion of Rabbi Natan, as it is taught in a baraita: Rabbi Natan says: Anyone who vows, it is as if he has built a personal altar, which is forbidden because one must bring all offerings to the Temple. And one who fulfills the vow, is as though he burns portions meant for the altar in the Temple upon it, i.e., the personal altar, thereby increasing his sin. Consequently, even after he has fulfilled the vow, it is preferable for him to ask a halakhic authority to annul it entirely, so that it will be as if he never took a vow.

§ The mishna stated that one who says: Wine is konam for me, and for that reason I will not taste it this week, is prohibited from drinking wine for the entire remainder of the week, including Shabbat. The Gemara poses a question: Isn’t it obvious that this is the case? The Gemara answers: It is necessary, lest you say that he said the days of the week, i.e., he meant for his vow to apply only on the weekdays. The tanna therefore teaches us that the phrase this week includes Shabbat.

The mishna stated: If one says: This month, it is forbidden to him for the entire remainder of the month, and the New Moon is considered part of the next month. The Gemara asks: Isn’t this obvious? The Gemara answers: When it was necessary to teach this halakha it was for a New Moon preceding a deficient, twenty-nine-day month. In such a case the New Moon is celebrated for two days, the first of which is the thirtieth day of the previous month and the second of which is the first day of the new month. The case here is one where he took the vow on the first day of the New Moon.

This is lest you say that the first day of the New Moon is part of the previous month, and therefore the vow should expire at the end of that day, and wine should not be forbidden to him during the upcoming month. The tanna therefore teaches us that since people call it the New Moon of the upcoming month, it is viewed as part of the upcoming month, and the vow applies to the new month.

§ The mishna states that if one says: This year, it is forbidden to him for the entire remainder of the year, and that Rosh HaShana is considered part of the upcoming year.

A dilemma was raised before the scholars: If one said: Wine is konam for me, and for that reason I will not taste it for a day, what is the halakha in his case? Is it considered as though he said today, and he is prohibited from consuming wine until nightfall, or is it considered as though he said one day, in which case the vow takes effect for a period of twenty-four hours?

The Gemara suggests: Come and hear a proof from the mishna: If one says: Wine is konam for me, and for that reason I will not taste it today, he is prohibited from drinking wine only until the conclusion of that day, at nightfall. The Gemara infers that this halakha only applies if he said the word today; therefore, if he said the vow applies for a day, it is considered comparable to a case where he said one day, and the vow is in effect for twenty-four hours.

The Gemara rejects this proof: But say the latter clause of the mishna: If he said that wine is forbidden to him for one day, he is prohibited from drinking wine from the day he took the vow to the same time on the following day. This indicates that it is only if he said: One day, that the vow takes effect for twenty-four hours; but if he said it takes effect for a day, it is comparable to a case where he said today, and the vow takes effect only until nightfall. Rather, no inference is to be learned from this mishna.

Rav Ashi said: Come and hear a resolution to this question from the following mishna (63a): If one vowed: Wine is konam for me, and for that reason I will not taste it this year, then if the year was extended, i.e., declared to be a leap year, he is prohibited from drinking wine in it and its intercalated month. The Gemara inquires: What are the circumstances?