The Israel Koschitzky Virtual Beit
The Laws of Shabbat
Yeshivat Har Etzion
Shiur #13: Cooking with Derivatives of Solar Heat and Using
a Solar-Heated Boiler Part 2*
By HaRav Baruch Gigi
Translated by David Silverberg
Prohibition of Toledot Ha-chama
In our last shiur we discussed the sugya in Masekhet
Shabbat (39a) where the Chakhamim and Rabbi Yossi argue as to whether
cooking with toledot ha-chama derivatives of solar heat is forbidden
on Shabbat. The Yerushalmi held
that one may cook with toledot ha-chama on Shabbat, and it writes:
[in Babylonia] they say that [cooking in] the sun is permissible, [but cooking
with] derivatives of the sun is forbidden.
The Rabbis here [in Eretz Yisrael] say that both [cooking with]
the sun and [cooking with] derivatives of the sun are permissible.
agree that cooking with toledot ha-chama does not constitute a Torah
prohibition; the debate surrounds the question of whether this is forbidden by
force of rabbinic enactment. We can
more readily understand this principle according to the approach (see last
week's shiur) that Torah law does not forbid cooking in the sun because
this method of cooking did not occur in the Mishkan, or because the term
bishul refers only to cooking with fire. According to these approaches, we can
explain that toledot ha-chama is likewise excluded from the Torah
prohibition because Chazal determined that this form of heat does not
constitute "fire" and this mode of cooking was not used in the
Mishkan. If, however, one
explains that bishul does not include cooking in the sun because of
shinui (deviation from the standard method of cooking), it is difficult
to understand why toledot ha-chama would not constitute a Torah
violation, whereas toledot ha-or derivatives of fire would violate
bishul. Cooking a food with
a garment that was heated in the sun seems to entail no more of a deviation from
normal procedure than cooking with a garment that was heated by exposure to
On the basis of this argument, Rav Shlomo Zalman Auerbach zt"l
(Minchat Shelomo, 1:12) dismissed this understanding, and contended that
the reason why bishul excludes cooking in the sun has nothing to do with
the factor of shinui:
Although Rashi wrote in
Shabbat (39a) regarding the fact that according to all views cooking in the
sun is permissible that this is because "this is not the standard method of
cooking," it nevertheless would seem that even in a manner which is commonly
used for cooking with the sun, such as a dud shemesh [solar-heated
boiler] and the like, one would likewise be exempt [from punishment], as we see
from the hot springs of Tiberias, that if we say that [the waters are heated by]
passing by the entrance to Gehinnom, it would constitute a derivative of
fire and [one] would be liable [for cooking with it]; otherwise, it would be a
derivative of the sun, and [one] would be exempt [from punishment if he cooks
with it]. Additionally, this
distinction between fire and the sun is mentioned also with regard to the
paschal offering, matza and challa, etc. and there it makes no
difference whether it is customary or not.
Necessarily, then, Rashi meant in his remarks that this is not called
explanation we mentioned that cooking in the sun is "natural" rather than
"human" cooking is the most
difficult to sustain in light of the exclusion of toledot ha-chama. This theory can stand so long as we deal
with cooking in the sun itself. But
when one cooks with a garment that was heated by the sun, this cooking is
clearly not a natural process; to the contrary, the individual harnesses the
solar heat for his needs, precisely as in the case of a garment heated by
exposure to fire.
I would therefore suggest that we explain this issue in the following
manner. The prohibition of
bishul requires a heat source, and this includes only the actual source
of the heat. Toledot
(derivatives) earn significance only insofar as they store within them the heat
of the original source. Hence, the
moment Halakha established that fire is the sole heat source with which
one violates the prohibition of bishul, all its derivatives likewise
become included, as they contain the heat of fire. But since the sun is not deemed a heat
source with respect to the bishul prohibition for the various reasons
mentioned in our last shiur its derivatives similarly do not qualify
for bishul, since they received all their heat from the sun, and we
cannot afford them a higher status than their source the sun itself.
The Yerushalmi, as stated, permits cooking with toledot
ha-chama. In the Bavli,
however, the majority view of the Chakhamim forbids cooking with a
derivative of solar heat because it might be confused with a derivative of
fire. We may suggest two approaches
in understanding this gezeira (rabbinic enactment):
1) Observers might mistakenly think
that the cooking is done with a fire derivative and thus suspect the individual
of violating Shabbat (mistaken identity of the item currently being used);
2) People might mistakenly conclude
that cooking is permissible with fire derivatives, as well (a mistaken halakhic
practical difference between these two explanations will arise in a case of a
derivative of solar heat that cannot be erroneously misidentified as a
derivative of fire, such as cooking on a hot rooftop, which quite obviously
received its heat from the sun, and not from fire. According to the first approach, we
would allow cooking on a hot rooftop, since nobody would suspect the individual
of cooking with fire; according to the second understanding, however, we would
forbid this form of cooking, as people may mistakenly allow cooking with
derivatives of fire, as well.
Rashi, commenting on this sugya, writes, "An observer will think
that it is a derivative of fire," clearly following the first explanation
mentioned above, and we should thus, according to Rashi, permit cooking on a hot
rooftop. One might, however,
respond that the Sages drew no distinctions between the various forms of
toledot ha-chama and forbade using it for cooking in all instances, even
where the reason for the basic prohibition does not obtain ("lo pelug
The Rambam explicitly applies this prohibition to all instances of
toledot ha-chama, without distinguishing between its various forms
(Hilkhot Shabbat 9:3):
breaks an egg in a hot garment, or in sand or dust from the roads, which had
become hot from the sun, even if it is roasted, he is exempt [from punishment]
because derivatives of solar heat differ from derivatives of fire, but [the
Sages nevertheless] forbade them out of concern for derivatives of fire.
forbids cooking even with sand or dust that was heated by the sun, which
obviously cannot be confused with a derivative of fire. This indicates that he either subscribed
to the second approach mentioned above, or felt that Chazal drew no
distinctions and extended the prohibition even to situations where the reason
does not apply.
The Gemara records a Berayta in which Rabban Shimon Ben Gamliel
allowed roasting an egg on a hot rooftop.
The question arises, did Rabban Shimon Ben Gamliel follow the view of
Rabbi Yossi, who permitted cooking with toledot ha-chama, or did he
follow the majority view, forbidding toledot ha-chama, and nevertheless
allowed cooking on a rooftop? Most
Sephardic Rishonim explain in our sugya that Rabban Shimon Ben
Gamliel followed Rabbi Yossi's position, but Halakha accepts the
Chakhamim's position, and thus all toledot ha-chama including
rooftops are forbidden. The
that which the Berayta states, "Rabban Shimon Ben Gamliel says, one may
roast an egg on a hot rooftop
" Halakha does not follow this view, for
he follows Rabbi Yossi. But the
Rabbis, who forbid [cooking an egg] with [heated] garments, would likewise
forbid [cooking] on a hot rooftop, since both constitute derivatives of the
Yerushalmi similarly indicates that roasting an egg on a rooftop would not be
permitted according to the view of "the Rabbis there" (in Babylonia), who forbid
cooking with toledot ha-chama:
Berayta disagrees with the Rabbis there, for the Berayta states:
"Rabban Shimon Ben Gamliel says, one may roast an egg on a roof of boiling hot
plaster, but one may not roast an egg on hot earth." What would the Rabbis there do with
this? They would answer that they
disagree with Rabban Shimon Ben Gamliel."
Yerushalmi thus explicitly asserts that Rabban Shimon Ben Gamliel disagrees with
the Chakhamim. The Meiri,
however, appears to maintain that Rabban Shimon Gamliel stated his
halakha even in accordance with the Chakhamim, as he writes, "But
[an egg] may be roasted on a hot rooftop, that was heated by the sun."
The Maharshal (Teshuvot, 61) elaborates on this topic and
concludes that we should forbid only those forms of toledot ha-chama that
could be mistaken for derivatives of fire.
He maintains that Rabban Shimon Ben Gamliel stated his view in accordance
with the Chakhamim, and they, too, would agree that one may cook on a
However, as far as the final halakha is concerned, since, as we
have seen, most Rishonim understood the Chakhamim as
forbidding all types of toledot ha-chama, we should follow this
stringent position. Indeed, the
Acharonim forbid cooking with any toledot ha-chama; see
Shulchan Arukh (318:3) and Mishna Berura (318:20). In situations of dire need however, we
may take into account the Maharshal's view; we will return to this point later,
in our discussion of solar-heated boilers.
Item that Had Been Cooked by the Sun or Derivatives of Solar Heat
The Peri Megadim (Mishbetzot Zahav, 318:6) raises the
question concerning a food that had been cooked before Shabbat by the sun or a
derivative of solar heat which does not constitute bishul on Shabbat
whether one violates Shabbat if he cooks this food on Shabbat over fire or with
a fire derivative. He concludes,
"It would seem that he is exempt, because it has already been impacted [=
prepared for consumption]; it might possibly be altogether permissible." The Peri Megadim's ambivalence
touches upon the question of whether cooking in the sun or a derivative of solar
heat is deemed "cooking" but nevertheless does not render one liable on Shabbat,
or is not classified as "cooking" at all.
According to the second possibility, we should perhaps equate an item
that had been cooked by solar heat with foods that can be eaten raw, to which
the prohibition of bishul applies.
We might also explain that the Peri Megadim here inquires as to
the meaning of the principle of ein bishul achar bishul (bishul
does not apply to previously cooked foods). Is this a practical rule, that once a
food has been prepared for consumption an additional act of cooking does not
qualify as food preparation? If so,
then we would apply ein bishul achar bishul even to foods that had been
cooked through solar heat, even if this type of cooking does not qualify as
"bishul" at all.
Alternatively, one might explain the principle of ein bishul achar
bishul as relating to an item's formal status as "mevushal"
("cooked"), in which case an item cooked in the sun if we assume that it
does not obtain the status of mevushal would not be subject to
bishul. The Peri
Megadim concludes that the food has the status of cooked food, and we
therefore apply the principle of ein bishul achar bishul.
The Iglei Tal (Ofeh, 44) held that cooking in the sun does
not qualify as "cooking" at all, even for purposes of cooking the korban
pesach,. He contended that if
one boiled a korban pesach in toledot ha-chama and then proceeded
to roast it, it is considered roasted and hence permitted for consumption. (Recall that a korban pesach must
be eaten roasted, and not boiled.)
Since Halakha does not classify cooking with solar heat as
bishul, the meat is considered only roasted. He writes (Ofeh, 15:9), "Since
cooking with the hot water springs of Tiberias is not considered bishul
with respect to the prohibition against [eating the korban pesach]
boiled, by the same token, if it is boiled [with this water] and then roasted,
it is permissible."
He linked this discussion to the issue of bishul on Shabbat on the
basis of the Yerushalmi (Shabbat 7:2), which records a debate if one may cook on
Shabbat with the hot water springs of Tiberias, and then applied this debate to
the situation of a korban pesach that was boiled in this water and then
roasted. The Iglei Tal thus
clearly felt that the status of cooking with solar heat on Shabbat, and its
status regarding the korban pesach, are dependent upon one another. In his view, then, if one would cook
over fire on Shabbat an item that had previously been cooked with solar heat, he
would violate bishul. The
rule of ein bishul achar bishul would not apply in such a case, because
this food had not previously undergone formal bishul.
The Iglei Tal's proofs are not compelling and may be refuted. Practically speaking, it would appear
that one may rely on the Peri Megadim's position, that one may cook over
fire food that had been cooked with solar heat. I found that the Minchat Chinukh
(mitzva 7) likewise addressed this question:
we say that it was, after all, cooked, only a gezeirat ha-Katuv
[ordinance of the Torah] dictates that one is not liable for [cooking with]
toledot ha-chama, but nevertheless in this respect it is considered
"cooked" in that a subsequent cooking would not be considered anything, and one
would be exempt? Or, since it does
not constitute cooking for purposes of Shabbat, it is thus not bishul,
and one would be liable [for cooking] afterwards.
ultimately leans towards relying on the aforementioned ruling of the Peri
Megadim, both with respect to Shabbat and regarding korban
Dud Shemesh on Shabbat
As we approach the issue of using hot water from a dud shemesh
(solar-heated boiler) on Shabbat, we must first clarify the technical facts and
then address two questions: Does the problem with a dud shemesh involve
cooking in the sun, or cooking with a derivative of solar heat, and do we
consider the entry of cold water into the dud shemesh the individual's
direct act, or merely gerama an indirect result of his actions?
The dud shemesh consists of a boiler into which cold water enters
from the household faucet (the entrance is located on the bottom side of the
boiler), from which it passes into black, glass-covered pipes called
koltim. The hot water then
enters the household's faucets from the upper part of the boiler, where the
water is hotter. Generally, the
departure of hot water from the boiler causes other, cold water to enter in its
place, which is heated in its initial encounter with the water already in the
dud, or when it is passed into the koltim.
questions concerning a dud shemesh:
1) If the cold water entering the
boiler is heated inside the boiler from the heat of the hot water already there,
then this clearly constitutes cooking with toledot ha-chama, which is
2) If the water is heated only when it
passes into the pipes, it would seem that this, too, involves cooking with
toledot ha-chama. We cannot
consider this process as cooking with the heat of the sun directly, which is
permissible, because the primary heating results from the heat of the pipes,
which became hot already before this water entered. Even if the sun would be concealed, the
pipes themselves would heat the water.
3) We discussed in an earlier
shiur that pipes through which hot water passes from a keli rishon
have the status of a keli rishon.
This would likewise apply in the case of a dud shemesh. Even though the heating process occurs
in the pipes, the entire system, including the pipes and the boiler, constitutes
a keli rishon and thus has the capacity to effectuate bishul. Recall, however, that we deal with
toledot ha-chama, so the bishul here is forbidden only
4) We must also take into account the
consideration that when one turns on a faucet he does not intend for cold water
to enter the boiler and be heated; his objective is strictly to release hot
water from the faucet.
opinion, none of these claims suffices to definitively allow using hot water
from a dud shemesh on Shabbat.
As far as the cold water entering the system is concerned, it would seem
that at least the initial flow of water would qualify as a direct act of the
individual, since by removing the obstruction one allows water to enter the
system. This situation would
resemble a case discussed in Masekhet Sanhedrin 77b:
Papa said: One who bound his fellow and directed the freshet towards him this
is his "arrows," and he is liable [for murder]. This applies only in [situations of] ko'ach rishon [a direct result of his action]; in
[situations of] ko'ach sheni
[a result of a result of his actions], this is merely gerama.
explains, "He turned the flow of water upon him; these are his arrows, and he is
considered as if he had shot an arrow at him." The same principle would seemingly apply
in our context. The initial rush of
water into the boiler would constitute ko'ach rishon, the direct result
of the opening of the faucet, and the individual would thus be considered as
having actually placed water into the system.
In truth, however, this conclusion is far from simple. Many Acharonim held that since
opening the faucet merely removes an obstruction, this cannot be deemed a direct
action, and rather constitutes gerama. In the case in Sanhedrin, the killer
actively channeled the flow of water towards the bound victim, whereas here, one
merely removes the valve which allows the water to flow. This might entail ko'ach sheni,
rather than ko'ach rishon.
And although Rav Ovadya Yosef (Yabi'a Omer, 4:34) writes that one
must be stringent in this matter with regard to Torah prohibitions, in this
case, perhaps, where we deal with the rabbinic prohibition of cooking with
toledot ha-chama, we might allow relying on the lenient positions, which
consider this a situation of gerama. This issue requires further
As far as the person's intent is concerned, the fact that he does not
intend to heat the new water is of no consequence; since the water will
invariably enter the system and be heated a case known as pesik reisha
the act would be forbidden
regardless of his indifference towards the heating of the water.
Nevertheless, Rav Ovadya Yosef (ibid.) discusses this issue at length and
permits using hot water from a dud shemesh, based primarily on two
A. We deal
with toledot ha-chama, with which cooking is forbidden
mi-de-rabbanan; therefore, those who follow the rulings of the
Shulchan Arukh may rely on his ruling that in instances of a rabbinic
prohibition, one may perform a pesik reisha an act that will
incidentally but invariably result in a melakha. The Shulchan Arukh issues this
ruling concerning a case of a knife that was thrust into a barrel before
Shabbat, where he permits removing and returning the knife, even though this
results in the expansion of the hole, thereby creating an opening to the barrel
(314:1). The Rama, however,
disagrees, and writes, "[This applies] only if he also removed it once before
Shabbat; but if he had not removed it before Shabbat, it is forbidden because it
is a pesik reisha, as he creates a hole and opening for the barrel." The Acharonim understood this
debate as revolving around the issue of whether we permit a pesik reisha
where the violation that results from the given action is only of rabbinic
origin. The Mishna Berura
knife] is thrust tightly, such that as a result of its removal and placement it
is certain that the hole will expand.
Nevertheless, since the actual prohibition is only of rabbinic origin, he
[the Shulchan Arukh] holds that it is permissible, since [the individual]
does not intend for this [to occur].
The Rama here intends to disagree with him, [claiming] that [this is
allowed] only if he had removed it once before Shabbat, such that it thereby
expanded somewhat [already before Shabbat], and it is therefore not certain
[that it will expand when he removes the knife on Shabbat]. Otherwise, this is forbidden, because it
will certainly occur; for although this is an opening that is not made for
removing and bringing in [items through it], which is forbidden only
mi-de-rabbanan, as mentioned above, he [the Rama] maintains that a
pesik reisha is forbidden even with regard to a rabbinic prohibition.
B. Even if
we wish to abide by the view that forbids pesik reisha in cases of a
rabbinic prohibition, here we have more reason to rule leniently because this is
a situation of lo nicha lei the individual has no interest in the
resultant melakha. In such
situations, many authorities rule leniently when dealing with a rabbinic
prohibition. (See, for example,
Tosefot, Shabbat 103a.) However,
some Acharonim rule stringently even in such cases, and permitted a
pesik reisha de-lo nicha lei only when what is at stake is two rabbinic
prohibitions; this is the position of the Mishna Berura (337).
The reason why the case of a dud shemesh involves a situation of
pesik reisha de-lo nicha lei is, seemingly, because the boiler is
generally large enough to provide enough hot water for one's essential needs on
Shabbat: washing one's hands and face, washing infants and washing dishes. (Bathing one's entire body in hot water
is forbidden on Shabbat for other reasons.) Therefore, one has no need for
additional water to come into the boiler on Shabbat. On the other hand, one might contend
that a person has interest in additional water entering the system so he has hot
water ready immediately after Shabbat.
This question would thus touch upon the more fundamental issue regarding
the definition of nicha lei, namely, the status of an action in which a
person has interest, but not interest that concerns a Shabbat prohibition. This issue clearly requires more
thorough elaboration in a separate context.
Furthermore, one might argue that if the water is heated not immediately
upon entering the boiler (because the water on the bottom is not hot enough to
heat the incoming water), but only when it reaches the pipes, the heating of the
water occurs not through ko'ach rishon the direct result of the
individual's action but rather through ko'ach sheni an indirect
result. We would then classify this
case as gerama, and when dealing with a situation of a pesik
reisha resulting in a rabbinic violation through gerama, it stands to
reason that this should be allowed.
We might add yet another consideration for allowing use of a dud
shemesh, namely, the aforementioned position of the Maharshal, who held that
one may cook on Shabbat with a type of toledot ha-chama that cannot be
confused with fire or a derivative thereof. Of course, it is far from clear that use
of a dud shemesh cannot be mistaken for use of fire-generated heat, since
at times especially during the winter a person adds electric backing to the
heating process of the dud shemesh.
In summary, it would appear that the matter remains subject to dispute,
and we therefore conclude upon the following practical guidelines:
1) One should preferably refrain from
using hot water on Shabbat from a dud shemesh.
2) Those who do use hot water from a
dud shemesh on Shabbat have authorities upon whom to rely, particularly
given that we deal with a rabbinic prohibition.
3) Water from a dud shemesh may
be used on Shabbat for the purpose of bathing infants or for washing hands or
dishes if a person's hands are particularly sensitive to cold.
4) This entire discussion applies only
if there is no electric backing to the boiler. If electricity is involved, then we deal
with a possible Torah violation, even if the electricity is currently turned
5) Notwithstanding what we just
mentioned, if the boiler works only on electricity which is currently turned
off, and it is not attached to a central heating system, and one can be certain
that the water in the boiler is not hot enough to heat the new water that comes
in, one may turn on the hot water.
As mentioned, use of an electric boiler entails a possible Torah
violation, so one may employ this leniency only when he can ascertain beyond
reasonable doubt that the new water will not be heated.
6) Some recent water heating systems
are equipped with a mechanism that prevents new water from entering the
system. Most systems do not feature
such a mechanism, but one who knows for certain that he has such a system may
use the hot water without any concern, since no new water will enter the system
and be heated.
shiur is a continuation from last week's shiur, and should be
studied in conjunction with it.
It is not altogether clear from the Minchat Shelomo why cooking in
the sun is not considered "cooking."
He perhaps held like the view we cited from the Rambam and others that
the Torah prohibition of bishul pertains only to fire and its
The Maharshal (siman 61) adopted this understanding of the
who sees that toledot chama are permissible will then say that a
derivative of fire is likewise permissible, for with respect to derivatives the
onlooker will think that no distinction is drawn between them, because in the
end they are both heated through another item and it constitutes a subcategory
One might contend that the Meiri considered cooking on a hot rooftop
equivalent to cooking in the sun directly, rather than toledot ha-chama,
but this does not seem reasonable at all.
The Rif in this sugya brings several views among the
Amora'im in interpreting Rabban Shimon Ben Gamliel; now if Rabban Shimon
Ben Gamliel was following the view of Rabbi Yossi, which Halakha does not
accept, the Rif would have no reason to record in his work the Talmud's
discussions concerning Rabban Shimon's position. The Ramban explained, "
even though he
[the Rif] wrote the reasons [given by] Rabba and Rav Yosef for Rabbi Yossi in
order to explain our Mishna, with which Rabbi Yossi agrees." His answer is difficult to
understand. See also below, in our
discussion of the Maharshal's view.
We discussed this subject in an earlier shiur which dealt with the
issue of cooking raw fruits.
According to the Peri Megadim's conclusion, we would explain that
here one merely increases the food's temperature, whereas the taste of a fruit
undergoes a significant change through the process of boiling.
Compare this rationale with the formulation of the Tosefta
(Shabbat, end of chapter 15), "One may bake that which was already baked, and
cook that which was already cooked."
In his closing remarks, the Peri Megadim refers us to the next
se'if, where he addresses the topic of boiling an item that had been
previously baked. His intention,
perhaps, is to compare cooking with fire an item that had been cooked in the sun
to the case of boiling an item that had been previously baked. Clearly, however, there is no comparison
between the two cases: when one boils a previously baked item, the food's taste
changes as a result of the second mode of cooking from the taste of a baked item
to that of a boiled item.
Whereas we generally maintain that one violates a Torah prohibition if he
eats meat from a korban pesach that was boiled and then roasted, the
Iglei Tal contends that if one boiled it with the hot springs of Tiberias
and then roasted it, it may be eaten, since bishul does not occur with
derivatives of solar heat.
The Yabi'a Omer there discusses this issue at length.
See Yabi'a Omer, ibid.
most Acharonim, as mentioned earlier, rule against the Maharshal's view,
we may nevertheless include his position as one of several factors to allow
using a dud shemesh.