Understanding the עונת אביאסף (Part One)

לרגל שובבי”ם ת”ת תשע”ו

Abstract: This essay will explore the Halachic basis for the עונת אביאסף and in the process will address various idiosyncratic curiosities  particular to וסתות and will attempt to shed light on them.

Many Ashkenazic Jews are aware of the עונת אור זרוע, but people are much less familiar with the עונת אביאסף. This is despite the fact that עונת אביאסף arguably has a stronger Talmudic basis[1]. So what is the עונת אביאסף?

While its practical application is a matter of dispute, simple put, the עונת אביאסף is the assertion that the עונת הוסת is always 12 hours of equal length[2]. While according to most authorities the עונת הוסת is either from sunrise (נץ החמה) to sunset (שקיעת החמה) – the אביאסף asserts that this is only true around the equinoxes (ימי ניסן ותשרי) when the days and nights are equal in length and both 12 hours – When the day and night are not equal (ימי תמוז וטבת) the עונה should be calculated as half the night and half the day, thus making the עונה consistently twelve hours. This question of the length of the עונה sheds some light on some of the more perplexing aspects of הלכות וסתות.

וסתות, while they correspond roughly to calendar days, there are some things about them that just don’t seem to jive with our notion of a halachic “day”. Firstly, while most “calendar days” are units of 24 hrs consisting of a day and a night, an עונה is either a day or a night, if an אשה sees on the same calendar day, but not consistently during the day or during the night – there is no וסת. Secondly, and perhaps more striking, is the fact that the “daytime” and “nighttime” for וסתות are defined differently than the “daytime” and “nighttime” anywhere else in הלכה. Generally speaking, the day starts at עלות השחר (dawn) and ends at צאת הכוכבים (the appearance of stars), for וסתות the day starts at נץ החמה (sunrise) and ends at שקיעת החמה (sunset). While we try to understand the עונת אביאסף, these idiosyncrasies will be addressed.

(This post will provide some background, we will deal specifically with the עונת אביאסף in subsequent posts.)

Okay, let’s start at the beginning, the משנה in the ninth פרק of נדה on דף סג ב which says:

היתה למודה להיות רואה בתחלת הוסתות כל הטהרות שעשתה בתוך הוסתות טמאות בסוף הוסתות כל הטהרות שעשתה בתוך הוסתות טהורות רבי יוסי אומר אף ימים ושעות וסתות היתה למודה להיות רואה עם הנץ החמה אינה אסורה אלא עם הנץ החמה רבי יהודה אומר כל היום שלה.

“If she was accustomed to seeing at the beginning of the (her[3]) וסתות all of the טהרות (items that she dealt with that demand ritual purity) that she handled during the וסתות are rendered impure. At the end of the (her) וסתות all of the טהרות that she handled during the וסתות maintain their purity. Rebbe Yosse says: also days and hours are וסתות. If she was accustomed to seeing with נץ החמה she is only forbidden with נץ החמה. Rebbe Yehuda says: the whole day is hers.[4]

The first part of the משנה is referring to an אשה who is accustomed to seeing with a וסת הגוף, (that is, her seeing always coincides with some other physical symptom or sensation, such as sneezing or hiccupping or a fever etc.) She is considered טהורה until the onset of these symptoms – if she generally has it at the onset of these symptoms, we can assume that it occurred as soon as the symptoms appeared and thus rendered whatever she was handling impure, if she generally sees at the end of these symptoms – the stuff she was handling at the onset can be assumed pure.

In the second part of the משנה we find a מחלוקת regarding the duration of an עונה. Rebbe Yosse holds that if an אשה is prone to seeing for a given hour – she is only אסורה for that hour – whereas Rebbe Yehuda holds that the עונה is always either a day or a night.

The גמרא continues:

היתה למודה: והתניא רבי יהודה אומר כל הלילה שלה לא קשיא הא דרגילה לראות בתחלת יממא והא דרגילה לראות בסוף ליליא תני חדא רבי יהודה אוסרה לפני וסתה ומתירה לאחר וסתה ותניא אידך אוסרה לאחר וסתה ומתירה לפני וסתה ולא קשיא הא דרגילה למחזי בסוף ליליא הא דרגילה למחזי בתחלת יממא אמר רבא הלכה כרבי יהודה ומי אמר רבא הכי והתניא והזרתם את בני ישראל מטומאתם מכאן א”ר ירמיה אזהרה לבני ישראל שיפרשו מנשותיהן סמוך לוסתן וכמה אמר רבא עונה מאי לאו עונה אחריתי לא אותה עונה ותרתי למה לי צריכא דאי אשמועינן הא הוה אמינא ה”מ לטהרות אבל לבעלה לא קמ”ל ואי מההיא הוה אמינא סמוך לוסתה עונה אחריתי קמ”ל אותה עונה.

“(The גמרא points out an apparent contradiction: The משנה says that if she was accustomed to seeing with נץ החמה Rebbe Yehuda says: the whole day is hers) but we have learnt in a ברייתא that Rebbe Yehuda says that the night is hers!? There is no contradiction, this one (the משנה) is referring to a woman that is accustomed to seeing at the beginning of the day, this one (the ברייתא) is referring to a woman who is accustomed to seeing at the end of the night.

(The גמרא will now use this solution to resolve another apparent contradiction) We learnt once (in one ברייתא) that Rebbe Yehuda forbids her before her וסת and permits her after her וסת and we have learnt in another ברייתא that Rebbe Yehuda forbids her after her וסת and permits her before her וסת!? There is no contradiction; this one is where she is accustomed to seeing at the end of the night (thus after the night Rebbe Yehuda permits her, but before her וסת – the whole night, he forbids her) and the other one is where she is accustomed to seeing at the beginning of the day (thus, until her וסת she is forbidden but afterwards she is permitted).

Ravva said: the Halacha is like Rebbe Yehuda.

(The גמרא then challenges this.) Did Ravva in fact say this? But we have learnt in a ברייתא as follows: “Thus shall ye separate the children of Israel from their uncleanness [5]” from here Rebbe Yirmia has said: This is a prohibition for the children of Israel that they must separate from their wives adjacent to their וסת. And how much is “adjacent”? Ravva said: an עונה. What does this mean? (It must mean) another עונה. No, it means that עונה. If so, why did Ravva have to tell us twice (he already said that the Halacha is like Rebbe Yehuda)? He had to tell us twice because if he only would have told us this one (the Halacha is like Rebbe Yehuda) I would’ve thought that this is only regarding items that must be handled in ritual purity – but not regarding her husband, and if from that one (the ברייתא of Rebbe Yirmia) I would’ve thought: what is an עונה? (It must mean) a different עונה; so this come to teach you that it refers to that עונה.”

Here we have our source that the length of an עונה is a day or a night; that one must refrain from תשמיש and handling טהרות for the duration of the עונת הוסת, and that the daytime עונה starts at נץ החמה.

To be continued…




[1] What I mean is that it doesn’t seem to contradict a גמרא מפורשת and there are even some proofs to the validity of its claims.

[2] In Halacha there are two different definitions of an hour, the common hour is a שעה זמנית, a temporal hour, the length of this hour is calculated by dividing the length of the daylight by twelve and doing the same to the night. Obviously, the length of each daytime or nighttime hour will vary seasonally. They will only be equal in length at the equinoxes. Things such as prayer times; times for burning חמץ on פסח; times for שבת and יו”ט; times for offering daily sacrificial offering etc are all determined based on שעות זמניות. The other version of an hour is called the שעה שוה, the “equal” hour; this is less common and generally used for things that are unrelated to the time of day. We will learn more about both definitions later.

[3] Parentheses are the author’s additions inserted for clarity purposes.

[4] Caveat Lector: All translations are the author’s unless specified otherwise.

[5] Leviticus 15:31 King James Version 😉


Rabbi, web developer, banjo enthusiast and dad blogging about whatever interests me at the moment.

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