Nedarim 120

Said Abaye to him: If so, let 'One day' be forbidden on account of 'to-day'?<span class="x" onmousemove="('comment',' I.e., if he vows 'one day', let him be forbidden until the nightfall of the following day. Otherwise, if he terminates his vow in the middle of the day, twenty-four hours after its commencement, he may think that had he stated 'today', he could likewise end it in the middle of the day of his vow. ');">¹</span>

— He replied: 'To-day' may be mistaken for 'one day', but 'one day' cannot be mistaken for 'to-day'.<span class="x" onmousemove="('comment',' I.e., if he vows 'one day', he may think that it ends at nightfall, just as 'to-day'; but if he vows 'to-day', he cannot possibly think that it ends before the nightfall of the same day, since in 'one day' the vow lasts beyond nightfall and includes part of the following day too. ');">²</span>

Rabina said: Meremar told me: Thus said your father in R. Joseph's name: With whom does this statement of R. Jeremiah b. Abba agree? With R. Nathan. For it was taught: R. Nathan said: Whoever vows is as though he built a high place, and who fulfils it, is as though he burnt incense thereon.<span class="x" onmousemove="('comment',' I.e., because one does wrong in vowing at all, he is treated stringently and ordered to obtain absolution for his vow when it should lapse automatically. In Rashi's opinion, this conflicts with the reason given by R. Joseph. But Asheri regards it as complementary thereto: whilst accepting the reasoning, he regards the fear of mistaking 'to-day' for 'one day' as insufficient in itself to justify this precautionary measure: hence he adds the reason drawn from R. Nathan's dictum. ');">³</span>

THIS SABBATH, HE IS FORBIDDEN THE WHOLE WEEK [AND THE SABBATH BELONGS TO THE PAST]. This is obvious? — I might think that he meant the [week] days of the Sabbath:<span class="x" onmousemove="('comment',' The Sabbath being a day of delight, it might be assumed that he never intended to deny himself wine on that day, since week-days too are implied in that term. ');">⁴</span>

we are therefore taught [otherwise].

'THIS MONTH,' HE IS FORBIDDEN THE WHOLE OF THAT MONTH, BUT THE BEGINNING OF THE [FOLLOWING] MONTH BELONGS TO THE FUTURE. This is obvious? — It is necessary only when the [following] Month is defective: I might think that the new Moon belongs to the past, and is forbidden: it is therefore intimated that people call it new moon.<span class="x" onmousemove="('comment',' The months of the Jewish year consist of either twenty-nine or thirty days and generally alternate. Hence, if the following month is detective (i.e., of twenty-nine days), this one is full. In the month following a full one, the first two days are designated 'new moon', the first being really the thirtieth day of the past full month. Hence, if one vowed in a full month, it might be thought that he is bound on the first new moon day of the next. Therefore the Mishnah teaches that since it is called new moon, People generally regard it as part of the next month, and hence he is permitted thereon. — This is the reading of Asheri, Ran and Tosaf. But our editions, and Rashi too. have: I might think that the new moon belongs to the past, and should not be forbidden. This reading cannot be reconciled with the first interpretation of the Mishnah, but agrees with the second (q.v. p. 190, n. 5). If he vowed 'this month' on the first new moon day, I might think that since it actually belongs to the past month he is not forbidden thereon. Therefore it is taught that since it is designated new moon, he must have meant to include it. ');">⁵</span>

'THIS YEAR,' HE IS FORBIDDEN THE WHOLE YEAR. The scholars propounded: What if one vows, 'Konam, if I taste wine a day'? is its law as 'to-day' or 'one day'? — Come and hear [a solution] from our Mishnah. 'KONAM, IF I TASTE WINE TO DAY HE IS FORBIDDEN WINE ONLY UNTIL IT GETS DARK; hence 'a day' is as 'one day'! Then consider the second clause: IF HE SAYS, 'ONE DAY,' HE IS FORBIDDEN FROM DAY TO DAY: hence a day' is as 'to-day'?<span class="x" onmousemove="('comment',' In Heb. 'one' is expressed by [H], but the indef. 'a' is unexpressed, lit., 'day', and hence the problem, and the differentiation between 'a day' and one day'. ');">⁶</span>

Thus nothing can be deduced from this.

R. Ashi said, Come and hear: 'Konam, if I taste wine this year,'<span class="x" onmousemove="('comment',' Lit., 'the year'. ');">⁷</span>

if the year was intercalated, he is forbidden for the year and the extra month. How is this meant?