Pesachim 74-76 Science,Torah and מחלוקת מציאות

A major theme of the beginning of פרק כיצד צולין  is the requirement that the קרבן פסח  be                  “צלי אש ולא צלי מחמת דבר אחר” (roasted by fire and not by anything else.)

This is derived from the double mention of the word “צלי אש”  in the פסוקים  (Shmos 12), which teaches us that not only must the קרבן פסח  be roasted by direct flame and not the heat of the vessel or liquid , but even things that might be considered the same as fire for other things requiring a fire  (such as a מכוה -leprous burn-which may come even from burning metal), are not considered as fire for the קרבן פסח , except for an actual flame itself.

As such, the פסח  may not be roasted with a metal spit, or through direct contact with the walls or floor of the oven, as part of the roasting process would then be performed by the heat of the metal spit or of the oven surface, and not directly by the fire.

There is much discussion regarding  the scope of these rules, during which some essential principles of אסור והתיר (contact between forbidden and permitted foods) is derived.


One of the most important rules pertains to how permitted items that have absorbed the taste of forbidden items may be freed of their forbidden status, namely the rule of “כבולעו כך פולטו”- in the same way that the forbidden taste is absorbed, so it is expelled.

A common application of this rule is that vessels that were used for roasting non-kosher food over a flame without liquid require לבון (direct, dry heat of a flame in order to be koshered.)

In contrast, vessels that were exposed only to hot liquids or foods cooked in liquids may generally be koshered by הדחה  (immersion in boiling water.)


Two other important rules are subject to debate.

  1. חם מקצתו חם כולו- when it comes to metal items (which conduct heat), if part of the item is hot, the entire item is viewed as hot. This is the view of the Mishna on daf 74a which forbids using a metal spit for roasting the קרבן פסח , assuming that the part of the metal spit inside the animal though less exposed to the fire is heated by the part outside it , something disputed by Rabbi Yehuda in a Beraisa brought by the Gemara on daf 74a.
  2. תתאה גבר – When a hot kosher or non-kosher item makes contact with a cold item of the opposite halachic status , do we view this stringently as hot contact, or leniently as cold contact?

It depends on whether the hot item is on top or on the bottom, but the rule is still subject to debate. רב  rules that עילאה גבר  – the item on top prevails. This means that if the item on top is hot, the contact is treated as hot contact, whereas if the item on top is cold, it is treated as cold contact.

In contrast, שמואל  holds that  תתאה גבר, the bottom item prevails- if the bottom item is hot, is is treated as hot contact whereas if the bottom item is cold, it is treated as cold contact.

The Gemara on daf 76a brings various proofs from the Mishna on daf 75b for the view of רב but they are all rejected. It then brings 2 proofs from ברייתות in support of Shmuel, seemingly given him the last word (see Rashi ד”ה “ושמואל who indeed rules this way), but clarifying that even if the cold item is on the bottom item, it is not treated exactly the same as cold contact but rather more leniently that hot contact- the kosher item is not rendered non-kosher in its entirely but the section of it that came in direct touch with the non-kosher item on top requires קליפה (peeling off)- see Tosfos ד”ה “תניא”  who discusses the situation where the kosher item is liquid and cannot be “peeled.”)

Both the above disputes share the common property that they appear at face value to be based on מציאות (factual matters) that can be easily tested.

The question of whether part of a metal spit being hot causes the rest of it to become hot is a scientific question easily answered by experimentation, as is the question of whether the top or bottom item being hot causes the two items to absorb taste from one another.

In truth, the scientific observation that hot air rises seems to indicate that if the hot item is on the bottom, it imbibes taste into the upper cold item but not the other way round, regardless of whether the permitted item is on the bottom or top, something which neither רב  nor שומאל  seem to acknowledge.

For example, if a cold kosher item is on top of a hot non-kosher item, then the taste of the hot non-kosher item should rise and be absorbed into the cold kosher item on top, as שמואל  indeed holds.

However, if a cold non-kosher item is on top of a hot kosher item, then from a scientific point of view, it seems that there is no way for the cold non-kosher item’s taste to rise and be absorbed into the hot kosher item below and besides for the area of direct contact which might require קליפה, there seems to be no reason to forbid the upper cold kosher item- yet שמואל  would indeed forbid it in this case too, seeing as the important factor to him is whether the hot item is on the bottom or not, not whether it is the kosher item or the non-kosher one!

In the world of  למדנות (lomdus or analytical learning), we generally try to avoid interpreting such disputes superficially and search for a more conceptual basis to the argument.

Additionally, although there might be some debate amongst the ראשונים  regarding how to relate to statements of Chazal that appear to be based on the possibly faulty science of their time, these both seem to be easily observable rules which are not dependant on relatively modern scientific research!

Perhaps one can suggest that the first dispute does not resolve around whether the part of the metal spit in direct contact with the animal is heated by the part of it that is exposed to the flame, but whether the degree of heating is considered sufficient for us to consider the animal as being roasted partly by the spit and not roasted in its entirety directly by the fire as required.

We see what might be a similar  distinction when it comes to the distinction of cooking in a כלי ראשון  on Shabbos  as opposed to cooking in a כלי שני.

Although the contents of the כלי שני  could be just as hot as the contents of a כלי ראשון , certainly to the point of יד סולדת בו (the min temperature that water needs to be in order for one to quickly withdraw one’s hand from it after testing it, which serves as the minimum temperature required for cooking on shabbos.), the heat of the כלי שני  is considered secondary, being derived from the contents of the כלי שני  and thus has less power to effect the cooking process.

Similarly, Rabbi Yehuda could opine that even though the entire rod is hot, the unexposed part of the rod has gained its heat from a secondary source, namely the exposed part, and this lacks the energy to effect significant halachik cooking, thus not invalidating the direct flame-roasting of the קרבן.

In contrast, the mainstream view rejects this parallel because unlike the כלי שני  whose contents might be just as hot but which itself lacks heat and thus absorbs the heating energy of the contents sparing  anything else placed inside it from the halachik cooking process, the unexposed part of the spit is constantly absorbing new heat from the exposed part, and thus far more capable of effecting halachik cooking to the קרבן, thus invalidating the direct flame roasting.

Even if this analysis passes scientific rigor, or if we accept that halachik definitions are not always the same as scientific, it seems harder to take such an approach in the second dispute.

Here the question is clearly not whether the type of heating caused by  a fixed degree of heat is halachically considered cooking or not, it is about whether the bottom item or the higher item is significant in determining the results of the contact.  This seems to be a מחלוקת מציאות by definition!

While searching the Responsa Project for Achronim who might discuss this issue, I came across a פרוש  on Pesachim by Rav Shlomo Ganzfried (פני שמואל פסחים עו.) , the famous author of קצור שולחן ערוך , who points to a תשובה (responsa) of the נודע ביהודה (קמא יו”ד כח) who asks this precise question.

While pointing out that there are many similar debates in matters of אסור והתיר  that appear to be מחלוקת מציאות that can be easily resolved by experiment, he notes that these debates where never resolved that way.

For example, אhere is famous debate (Chullin 98a) whether forbidden foods are בטל בשישים  (nullified) by 60 times the quantity of permitted foods) or only בטל במאה (nullified by 100 times the quantity.)

This too seems to be a מחלוקת מציאות  as the main issue is whether the אסור  imparts of its taste to the התיר  when the היתר  is more than 60 but less than 100 times the אסור.

The same question can be asked regarding the debate whether מליח כרותח  (salting is like boiling.)

He presents the thesis that the rules of when taste is transferred are not based on objectively proven criteria, as just because an item is able to impart taste, it does not always do so.

Chazal set certain thresh-holds based on what appeared logical to them,  that determine when we are חושש for this happening, but that does not mean that every time there is less than 60 times the אסור  taste is always imparted or vice versa.

As such, ascertaining these things is hard enough to do via experimentation that debates around them are a justified form of מחלוקת מציאות .

How the availability of modern statistical sampling methods might improve our ability not only to experiment but to assess how significant the results of the experiments are is not addressed in the נודע      ביהודה, and opens questions which are beyond the scope of this post.

These posts are intended to raise issues and stimulate further research and discussion on contemporary topics related to the daf. They are not intended as psak halacha.

Pesachim 69-70 The Pesach night Chagiga and the egg on the seder plate

The Mishna on 70b tells us that the  קרבן חגיגה   (festive sacrifice) brought together with the קרבן פסח  was not subject to many of the rules that the קרבן פסח itself was subject to:

Unlike the קרבן פסח  which could only be a male goat or lamb, under two years of age, the חגיגה  could come from cattle as well, and be female or male, younger or older than two years.

Furthermore, unlike the קרבן פסח  which only had one day and one night after its slaughter to be eaten, the חגיגה  may be eaten within two days and one night.

However, unlike the קרבן פסח which was always brought, the חגיגה  was neither brought on Shabbos, nor if most of the community was impure, nor if the group associated with the קרבן פסח  was small enough to be satisfied by the קרבן פסח   itself.

The Gemara deduces from this that the author of the Mishna holds that the חגיגה  is not obligatory- After all, if it was obligatory, it should be offered on shabbos like all obligatory sacrifices with a fixed time.

We should note that the Gemara uses the language “לאו חובה היא”  (is not obligatory) to describe the special chagiga of Pesach night.

The simple meaning of this means that although it could be דאורייתא (biblical in nature,) it is a voluntary mitzva and not an obligatory one.

Yet it is not the norm for the Torah to give us voluntary mitzvot without specifically saying so, and we also do not usually  דורש טעמא דקרא (expound the verse’s reasons, a topic for another post, but see meanwhile Sanhedrin 21a ) and conclude that a mitzva in the Torah does not apply when the reason does not seem to apply.

It is thus not surprising that the Tosfos understand that the Gemara means to say that it is only  דרבנן (a rabbinical command.) and that this is why it cannot push aside the prohibition of melacha on shabbos.


The Gemara proceeds to bring a Beraisa that explains that the חגיגה  is eaten first in order that the קרבן פסח  can be eaten על השובע  (while satisfied.)

Rashi understands that the reason the קרבן פסח  in turn needs to be eaten על השובע  is ” שיהו נהנין באכילתו ותיחשב להם” (so that they should get pleasure from eating it and it should be significant to them.)

He seems  to understand the phrase על השובע  not literally as “while fully satisfied” but rather as while not very hungry, or partly satisfied.

The חגיגה  thus plays the roll as a filler in order that the relatively small amount of meat that each member of a large group gets from the קרבן פסח will be eaten after one has already satisfied his hunger and be able to relax and enjoy it- after all, even though it is clearly not healthy, one who is very hungry often tends to eat quickly in order to satisfy his hunger and doesn’t take the time to enjoy his food properly.

In contrast, the Tosfos quotes the ריב”א  based on the Yerushalmi as explaining that this requirement is a גזירה דרבנן  (rabbinical decree) to prevent one from rushing to eat it in his hunger and while doing so, transgressing the prohibition of שבירת עצם (breaking a  bone of the קרבן פסח.)

Whereas it is אפשר  (possible), though not  מוכרח  (a foregone conclusion)  that Rashi views על השובע to be an intrinsic element in the mitzva of קרבן פסח, without which one might not fulfil one’s obligation, the approach brought by Tosfos clearly sees it as a side- requirement on a rabbinical level, which probably, though not certainly, would not מעכב (hold back) one’s fulfillment of the mitzva.


Back to the Beraisa quoted by our Gemara, we should note that it does not bring the requirement that the קרבן פסח  be eaten על השובע as the reason that the חגיגה is brought in the first place but only as the reason why it is eaten before the קרבן פסח – it is the Gemara that seems to goes further and take this as the reason for bringing the חגיגה , and thus the reason why the חגיגה  is not brought by small groups.

We should note that all the above applies to the special חגיגה  brought on erev Pesach and eaten on the night of Pesach, and not to the regular obligatory חגיגה  brought on the first day of Pesach and other festivals.

Whereas it is not yet clear whether  the regular חגיגה can be brought by an impure community, it seems implicit at this stage that being דאורייתא ,it is brought on shabbos, and certainly isnt dependant on the number of people eating it.

 However, on the next amud, Rav Ashi derives from a passuk that the regular chagiga is also not brought on shabbos. This seems to clash with our Gemara’s deduction from the fact that the חגיגה  brought with the פסח is not offered on Shabbos, that it is not obligatory- after all, the regular חגיגה  is certainly obligatory yet it is also not brought on shabbos!

Tosfos suggests that even if the חגיגה  brought with the פסח  is דאורייתא, it cannot be compared to the regular חגיגה which does not have a strictly fixed time and unlike it can be offered on all 7 days if missed on the first day!

As such, it  is only regarding the חגיגה  brought with the פסח that the Gemara claims a causal link between biblical level obligation and the ability to overide the prohibition of מלאכה  on shabbos!


The Gemara continues to note the dissenting view of בן תימא who holds that the  חגיגה  that comes with the קרבן פסח  is subject to the same time restrictions that apply to the קרבן פסח , and only the regular חגיגה brought on Pesach day enjoys a  less restrictive time-period for it to be eaten.

In support for his view, the passuk “ולא ילין לבקר זבח חג הפסח”  is brought, where the word “זבח” is taken to refer to the חגיגה and “פסח”  to refer to the קרבן פסח.

The implication, as noted by Tosfos, is that בן תימא  considers the חגיגה to be דאורייתא whereas the חכמים  of the Mishna who disagree with him, consider it to be דרבנן.

After much discussion, the Gemara  also concludes that according to בן תימא, all or most of the other restrictions pertaining to the קרבן פסח also apply to that חגיגה.

Tosfos points out that later (Pesachim 71a) the Gemara brings a פסוק  to prove that the חגיגה may be eaten for 2 days and one night, unlike the קרבן פסח which clearly seems to support בן תימא  against our Mishna as saying that the חגיגה  is דאורייתא  and thus offered on shabbos as well!

He also notes that there is a view elsewhere (Chagiga ) that implies that the  חגיגה   of ערב פסח  is indeed דרבנן, and we are left with aמחלוקת תנאים  regarding whether

  1.  the חגיגה  on ערב פסח  has the same biblical status as the regular חגיגה  AND is offered on pesach as well


 whether it is simply a מצוה דרבנן  designed to ensure that the rule that the קרבן פסח  is eaten while partially satisfied is upheld AND is thus NOT offered on shabbos.


Although we do not merit to bring either the קרבן חגיגה  or the קרבן פסח in our time, there are a number of possible practical ramifications of the above analysis, one of which I wish to bring up briefly:

The egg which is traditionally placed on the Seder plate is done so  זכר לחגיגה (see Orach Chaim 473/4 based on Tur O.C. 473 but see also other views brought, all based on Pesachim 114b.)

It seems that according to the view that חגיגה  on Pesach night is only דרבנן and not brought on shabbos , when Pesach falls on Shabbos, the egg should not be placed.

Although some Rishonim do indeed rule this way, the halachik consensus seems to be that being just a זכר  and also due to other reasons given for using the egg, we do so anywhere (see above sources for more details.)

These posts are intended to raise issues and stimulate further research and discussion on contemporary topics related to the daf. They are not intended as psak halacha.

Pesachim 67-68 טומאה הותרה בצבור , bringing sacrifices in our day, and visiting Har habayit

One of the main (though not the only) halachik impediments to visiting the Temple Mount as well as offering up the קרבן פסח  in our day is the fact that in the absence of a פרה אדומה (red heifer), whose ashes are biblically  required for purifying a טמא מת , we generally assume that we have this status and are thus not permitted to enter or offer or eat  the קרבן פסח  and risk the severe penalty of כרת  for doing so.

It should be noted that it is clear from the discussion on daf 68 that a טמא מת is not prohibited from entering the entire הר הבית, which has the halachik status of the מחנה לויה  (Levite camp), but only from entering the area of the עזרה  (Temple courtyard) itself, which has the halachik status of the holier מחנה כהונה (Priests camp.)

This contrasts with a זב  who is forbidden to enter the מחנה לויה  and a מצורע (leper) who is forbidden to the enter the entire camp of Israel.

Although the status of זב is not applied in our time, the related albeit less severe type of impurity known as טומאת קרי (impurity due to a seminal emission) also disqualifies one from entering the מחנה לויה  and thus the entire הר הבית  but can be removed by going to Mikva according to halacha before entering.

This is the practise of those who permit visits to the parts of הר הבית  known to have been outside the עזרה  itself, while the plurality of poskim who forbid or at least caution against doing so base their view mainly on the lack of certainty as to the precise place of the עזרה  and בית המקדש itself, a topic I hope to address in the future.

I would like to focus on a different but related question, that being whether it is permitted to offer up a קרבן פסח in our times, something which might theoretically require neither a rebuilt     בית המקדש  (see Zevachim 107b) nor a פרה אדומה, as we shall see.

It goes without saying that this would be provided all other halachik issues have been resolved , such as the status of today’s kohanim, the possible requirement for a kohain gadol, the need for the special garments to be worn, etc. (for a detailed discussion on the topic, see the article by  מורי וידידי haGaon haRav Gavriel Saraf   שליט”א on

It also assumes that this is physically and legally possible, without endangering lives, as however seriously this קרבן  is taken in halacha, it does not override the laws of פקוח נפש  (the question of שעת הגזירה and whether this applies to our situation is beyond the scope of our discussion.)

Having shown that the תמיד  (daily communal burnt offering) and קרבן פסח  (Passover offering) are both performed on shabbos, overriding the prohibition of melacha, the Gemara turns to another powerful property of these sacrifices, namely their ability to override the rule of טומאה  (impurity) provided that  the majority of the community is impure.

Usually speaking, a person who is טמא מת (impure due to contact with a corpse) is not permitted to bring the קרבן פסח, just like other קרבנות, and rather brings his קרבן  one month later  on פסח שני  when his טומאה  has passed.

However, the Mishna (Pesachim 76b) tells us that the קרבן פסח  may both be brought and eaten in impurity if the majority of the community is impure, and of course entering the עזרה  while impure in order to perform the offering must thus also be permitted for the kohanim.

As such, the fact that we are all assumed to be טמא מת  and unable to leave that status due to the lack of a פרה אדומה should theoretically not stand in the way of bringing a קרבן פסח  in our time!

On daf 66b,the Gemara derives via the same גזירה שוה that Hillel used regarding shabbos, that the תמיד  may also be brought under those conditions, though being an עולה, it obviously is not eaten (see Tosfos 66a ד”ה “מה” who discusses other possible sources for this.)

On daf 67a, The Gemara concludes that the source that theקרבן פסח   itself may be offered while impure if the majority of the community are impure comes from the law of פסח שני  itself.

Regarding פסח שני, the פסוק  ( Bamidbar 9/10) states “איש איש כי יהיה טמא לנפש ”  – (any man who will be impure from a life .)

From the phrase “איש איש”  , we derive that only an individual who is impure needs to put off his קרבן  till פסח שני  but if the community in whole or majority is impure, the קרבן פסח  is offered as usual on Pesach itself!

From the word לנפש, it derives that this concession applies only to טומאת מת  and not to other forms of impurity.

Although there are other forms of impurity that affect many or most of us today, the most common being טומאת קרי (impurity due to a seminal emission), these impurities can be resolved through mikva without the red heifer’s ashes and need not stand in the way of קרבן פסח.

As such, should all the other issues be resolved, neither the lack of a Beis haMikdash, nor the issue of impurity seem to stand in the way of bringing a קרבן פסח  today, and given the severe penalty for not doing so, it seems at first glance that we should obligated to do whatever we can do make this possible.

Many of us feel extremely uncomfortable with the idea of returning to what might seem like a primitive and barbaric form of worship, and there might even Torah sources that seem to back up such discomfort, a topic for another occasion.

Yet, as Moreinu haGaon Rav Asher Weiss שליט”א  once said to me over a barbecue in Africa while we were discussing this subject, its is rather hypocritical to sit eating a steak and criticize sacrificial worship- after all if one is comfortable with slaughtering an animal for one’s own pleasure, why would one be uncomfortable with doing so as part of the Torah mandated divine worship?

Of course, one could argue that whereas human beings NEED sustenance, and meat  has been viewed through most of history as an important form of sustenance, Hashem certainly does NOT need it, and there should be better ways to show our dedication to him than killing his creatures and offering them to him.

Yet it is axiomatic that Torah practices tend to be very symbolic and use methods of divine service which people can relate too-The fact that Hashem has no need for anything does not stop us from showing our appreciation of him by offering up that which is valuable to us and seeing as meat is  a major source of sustenance and pleasure for most of us, the above argument is rather mute.

When it comes to the קרבן פסח, this argument falls away completely , seeing as this unique korban is primarily about us eating it .

Almost all of us enjoy our lavish meat meals on Seder night, so why would we be opposed to first dedicating the very meat we are about to eat to Hashem?

Those people who are “religiously” vegetarian and are against killing animals at all even for food, or claim that meat is no longer needed for sustenance might indeed hold the moral high ground needed to at least start this discussion, but it seems like the rest of us should really grow up and prepare for the time when we will at least be able to fully dedicate our lust for meat to Hashem before eating it, a time which might virtually be here already, at least once a year!

יהי רצון מלפניך שיבנה בית המקדש במהרה בימינו ותן חלקינו בתורותיך ושם נעבדך ביראה כמי עולם וכשנים קדמוניות. “וערבה לה’ נמחת יהודה וירושליים כימי עולם וכשנים קדמוניות.”

These posts are intended to raise issues and stimulate further research and discussion on contemporary topics related to the daf. They are not intended as psak halacha.