One of the unusual features in this year’s Jewish calendar is that the first day of Pesach is Sunday, so Seder will be on Saturday night. This is actually not as unusual as everybody thinks — it would be more accurate to say that any other day of the week when Pesach falls is unusually common, rather than saying that Pesach falling on Sunday is unusually rare.
Let me explain what I mean by that. If the calendar always followed the astronomical facts, there would be no reason for Pesach (or any other specific date) to fall on any given day of the week more than any other, so it would fall on each day on average one year in seven. However, there are only four days when it can fall: לא אד”ו ראש, לא בד”ו פסח (lo ido rosh, lo badu pesahh): Pesach can never be on Monday, Wednesday, or Friday.
Trivia question: why do I transliterate that lo ido rosh, not lo adu rosh, the way almost everybody pronounces it?
So, on years when the actual full moon would be Monday, Wednesday or Friday, Pesach is postponed to Tuesday, Thursday or Saturday respectively (to be precise, the following Rosh Hashana is postponed, but it comes to the same thing because the number of days from Rosh Hashana to Pesach is constant). Therefore, Pesach on Tuesday, Thursday or Saturday is twice as common as should it be, but Pesach on Sunday will only happen once in seven years according to the statistical average, with no extras caused by postponement from other days. It’s not quite as simple as that, because there are other reasons why Rosh Hashana gets postponed, so it’s not exactly once in seven years, but it’s pretty close. The table in the back of my Machzor gives the dates of Pesach from 1974 to 2024, and 8 out of those 51 are Sundays. The distribution, on the other hand, is very irregular: it happened last only 4 years ago, and is happening again in 3 years time, but after that the next occurrence isn’t until 2021.
Having Pesach on a Sunday, causes some interesting and unusual halachic situations throughout the year (see section M of the article I link to above for a list of 42 of them). Because of the comparative infrequency and the occasional long gaps, people are often vague about the details of these, and this is nothing new — this vagueness is what caused Hillel the Elder to be elected Nasi, Prince of the academy. It’s a story I’m very fond of; in fact this whole post has only been written as an excuse to lead up to it. It’s an elegant combination of typically Rabbinic hermeneutics set in a frame story which is like an archetypal myth of the riddle which nobody can answer until a young stranger appears, answers the riddle and marries the princess.
The riddle here is a halachic question, not one of the list of 42 but one which only applied in Temple times: if Pesach falls on Sunday, the 14th of Nisan when the Paschal Lambs were offered falls on Shabbat. Can the lambs be sacrificed on Shabbat or not? We take up the story on Pesachim 61a, right after the first Mishna of Chapter 6 (which has given away the answer to the riddle, so I won’t quote it):
תנו רבנן הלכה זו נתעלמה מבני בתירא.
פעם אחת חל ארבעה עשר להיות בשבת. שכחו ולא ידעו אם פסח דוחה את השבת אם לאו
אמרו: כלום יש אדם שיודע אם פסח דוחה את השבת אם לאו?
אמרו להם: אדם אחד יש שעלה מבבל והלל הבבלי שמו ששימש שני גדולי הדור שמעיה ואבטליון ויודע אם פסח דוחה את השבת אם לאו.
שלחו וקראו לו. אמרו לו: כלום אתה יודע אם הפסח דוחה את השבת אם לאו?
אמר להם: וכי פסח אחד יש לנו בשנה שדוחה את השבת? והלא הרבה יותר ממאתים פסחים יש לנו בשנה שדוחין את השבת!
אמרו לו מנין לך?
אמר להם: נאמר “מועדו” בפסח ונאמר “מועדו” בתמיד. מה מועדו האמור בתמיד דוחה את השבת אף מועדו האמור בפסח דוחה את השבת. ועוד קל וחומר הוא: ומה תמיד שאין ענוש כרת דוחה את השבת, פסח שענוש כרת אינו דין שדוחה את השבת?!
מיד הושיבוהו בראש ומינוהו נשיא עליהם והיה דורש כל היום כולו בהלכות הפסח.
This translation is based on Rodkinson, because it’s after midnight and I’m too lazy to do it from scratch. However, I’ve rewritten it a bit, because he totally loses the repetitive folk-tale style.
The rabbis taught: The Halakha in the Mishna was not known to the children of Bathyra; for it once happened that the 14th (of Nissan) occurred on a Sabbath, and they did not know whether the Passover sacrifices superseded the Sabbath or not. They therefore commenced to look around for a man who knew whether the Passover sacrifices superseded the Sabbath or not, and they were told that there was a man who had recently come from Babylon, called Hillel of Babylon, and who had learned under the two greatest men of that generation, namely, Shemaiah and Abtalion; he would know whether the Passover sacrifices superseded the Sabbath or not. They sent for him and asked him: “Dost thou know whether the Passover-sacrifice supersedes the Sabbath or not?” and he answered: “Have we only one Passover-sacrifice that supersedes the Sabbath? are there not over two hundred sacrifices that supersede the Sabbath?” (i.e., the continual daily offerings which are offered twice on the Sabbath and the additional two sacrifices which are brought especially on the Sabbath). But they insisted upon his basing his assertion upon some actual text, and he said: “As it is written concerning the continual daily sacrifice [Numb. xxviii. 2]: ‘My offering, etc., shall ye observe to offer unto me in its due season,’ and the same term, ‘at its appointed season,’ is mentioned in connection with the Passover-sacrifice [Numb. ix. 2]: just as the ‘appointed season’ of the daily sacrifice supersedes the Sabbath, so too the ‘appointed season’ of the Passover sacrifice supersedes the Sabbath. Aside from this analogous deduction, there is also an a fortiori conclusion; for if on account of the continual daily sacrifice, for the neglect of which the penalty of Kareth is not incurred, the Sabbath may be violated, then on account of the Passover-sacrifice, for the omission of which the penalty of Kareth is incurred, we must conclude that the Sabbath may be violated.” When they heard this, they immediately placed him at their head and made him a prince. Thereupon he sat all day and preached upon the Halakhoth of the Passover.
But now Hillel becomes too proud, makes an arrogant remark, and is immediately floored by a question he is unable to answer. In this version of the myth, at least, the hero recovers his humility and saves himself by appealing to the prophetic spirit of the whole nation.
התחיל מקנטרן בדברים. אמר להן: מי גרם לכם שאעלה מבבל ואהיה נשיא עליכם? עצלות שהיתה בכם שלא שמשתם שני גדולי הדור שמעיה ואבטליון!
אמרו לו: רבי, שכח ולא הביא סכין מערב שבת מהו?
אמר להן: הלכה זו שמעתי ושכחתי. אלא הנח להן לישראל אם אין נביאים הן בני נביאים הן.
למחר מי שפסחו טלה תוחבו בצמרו מי שפסחו גדי תוחבו בין קרניו.
ראה מעשה ונזכר הלכה, ואמר: כך מקובלני מפי שמעיה ואבטליון!
Subsequently Hillel began to reproach them, and said: “What induced you to set me up as a prince among you? Only your own idleness in not taking advantage of the learning of the two great men of your generation, Shemaiah and Abtalion.”
The following question was propounded to Hillel: “What is the law if a man had forgotten to bring the slaughtering knife on the day preceding the Sabbath?” He answered: “I have heard the Halakha but have forgotten it. Leave this, however, to the Israelites themselves, for though they are not prophets they are descendants of prophets, and they will know what to do.” On the morrow he noticed that those who brought sheep as a sacrifice had the knife thrust in the wool of the sheep and those that brought goats as a sacrifice had the knife stuck between the horns, whereupon he remembered the Halakha covering the case and exclaimed: “Thus is the tradition which I have received from my masters Shemaiah and Abtalion.”
The expression near the end הנח להן לישראל אם אין נביאים הן בני נביאים הן, Hanahh lahem leyisrael, im ein neviim hen benei neviim hen, has become proverbial, roughly equivalent to Vox populi vox dei.