The Grafted Etrog
Adapted by Yitzchak Ben-David
Translated by David Silverberg
Grafting, a widespread agricultural procedure, involves attaching a branch of a certain tree to a tree of a different species. It is particularly common to graft branches taken from cultivated trees onto wild trees, which are considered agriculturally stronger and more immune to botanical disease. Over the course of many generations, people would commonly graft branches of etrog trees onto lemon trees. We refer to an etrog grown in this manner as "etrog ha-murkav," or a "grafted etrog."
The Gemara never addresses the suitability of such an etrog for the mitzva of the four species on Sukkot. Nor do we find any Rishonim who address the issue. The discussions concerning this issue begin to appear only in the last several centuries. The Acharonim dealt with this question at length and gave different reasons to disqualify an etrog ha-murkav from use on Sukkot. We may classify all the different reasons under two general categories:
A) We disqualify the etrog because the identity of its species.
B) The etrog is invalid because of the prohibition that had been violated through the grafting procedure.
A. THE IDENTITY OF THE SPECIES
The first group of reasons for disqualifying this etrog works on the once widely-held assumption that grafting a branch onto a different tree changes the physical identity of the fruits grown from that branch. Alternatively, even if, from a purely botanical viewpoint, the host tree has no impact at all on the grafted branch, nevertheless, halakhically speaking, the branch loses its previous identity and takes on the identity of the host tree's species.
Accordingly, several problems arise concerning the possibility of using such an etrog for the mitzva on Sukkot. First, we cannot define this fruit as an etrog; it is considered a different species, which one cannot use for the mitzva of arba minim. Secondly, even if we can identify the fruit as an etrog, the involvement of the lemon tree in its growth renders it an "etrog chaser" - an incomplete etrog, as a portion of the fruit is lemon. Moreover, if we deal with an etrog of the minimum size required for the mitzva, we must subtract the lemon portion from its size, such that its size falls short of the minimum required size for the mitzva. Thirdly, since the fruit consists partially of a lemon, using it for the mitzva entails adding an additional species onto the arba minim, which constitutes a violation of "bal tosif" (adding onto mitzvot).
These three different arguments for disqualifying the etrog ha-murkav yield different practical conclusions. If we invoke the halakha of "chaser" as the basis for the etrog's disqualification, the disqualification would apply only on the first day of Sukkot, when halakha requires "lekicha tama" (a "complete" taking of the four species, to the exclusion of an "etrog chaser"). By contrast, if the authentic etrog portion in this fruit amounts to a less than a ke-beitza, or if we do not consider this fruit an etrog at all, then clearly it would remain invalid throughout the entire festival of Sukkot. However, Tosefot maintain that an etrog need not be the size of a ke-beitza, but must rather be large enough that "nikeret lekichato" – one can recognize it as it is held. According to this view, then, even an etrog ha-murkav no larger than the minimum required size would be valid after the first day of Yom Tov.
As mentioned, all these reasons presume that grafting alters the identity of the fruit and transforms it into a different species. If we accept this premise, then we must conclude that even if the grafting occurred generations ago, all etrogim grown subsequent to the grafting cannot be used for the mitzva of arba minim.
However, modern botanical science has established with absolute certainty that the host tree has no impact whatsoever on the identity of the fruit grown on the grafted branch. The tree transfers water and minerals to the branch, but the genetic makeup of both the branch and tree remains unchanged. However, though this is undeniably the case scientifically, two primary sources in halakhic literature appear to indicate otherwise. We will deal with each of these two sources separately.
The mishna in Kilayim (1:7) cites a debate between Rabbi Yehuda and the Chakhamim concerning grafting:
"One may not merge a tree with a tree, a vegetable with a vegetable, a tree with a vegetable, or a vegetable with a tree. Rabbi Yehuda permits [merging] a vegetable with a tree."
This mishna is addressing the biblical prohibition of kilayim, mixing species. The Yerushalmi explains that in Rabbi Yehuda's view, Halakha forbids grafting only when it results in a new species. When one grafts a vegetable onto a tree, no new species is created, since the grafted vegetable does not blend with the tree's species but rather develops independently. Therefore, Rabbi Yehuda maintains that such grafting does not violate the prohibition. The Chakhamim, by contrast, hold that the prohibition does not depend on an actual merging of the species by creating a new species, and any form of grafting is forbidden by Halakha. This is how the commentary "Mareh Panim" understood the Yerushalmi's explanation.
It thus emerges that according to Rabbi Yehuda, in a situation of a tree grafted onto another tree, the branch draws all its sustenance from the host tree and the identity of its fruits changes. Rabbi Yehuda demands an actual blend of the species for the prohibition of kilayim to take effect, and he indeed forbids grafting trees together. Necessarily, then, he sees in the grafting of two trees the creation of a new species. However, according to the view of the Chakhamim, which is accepted as Halakha, the Torah forbids all grafting, regardless of the emergence of a new species. Therefore, we cannot reach any conclusions as to whether in their view the host tree impacts upon the identity of the branch's fruit.
It becomes clear from the continuation of the Yerushalmi's discussion that even the Chakhamim believed that the host tree impacts upon the fruit. The Yerushalmi says, "One may not graft olives onto a palm tree because this is [grafting] a tree with a tree… This case is different, because it will ultimately sweeten it." The Yerushalmi thus establishes that a palm tree hosting a grafted olive branch will have a sweetening effect on the olives produced by the branch. The Yerushalmi presents this statement as universally accepted, without limiting it specifically to Rabbi Yehuda. It appears, then, that the Chakhamim concur with this assumption.
We must therefore conclude that according to the Yerushalmi, the host tree changes the identity of the fruits grown on the grafted branch, and thus a branch from an etrog tree grafted onto a lemon tree grows not etrogim, but rather an etrog-lemon hybrid. Consequently, these fruits are unsuitable for use for the mitzva of arba minim. However, as mentioned, this conclusion runs counter to the findings of botanical science. Therefore, we should perhaps suggest a different reading of the Yerushalmi.
Agriculturally, grafting is done not for the purpose of merging two species, but rather to allow fruits that grow on cultivated trees, which are exposed to various diseases, to grow instead on wild trees, which are considered healthier and more immune to disease. The merging of two species occurs through natural or artificial pollination between the female cells of one species and the male cells of the other (crossbreeding). Grafting two species has the side effect of allowing for the possibility of cross-pollination between them, which creates a new species. In other words, the grafting itself does not create the hybrid, but it does bring the two species in close proximity to one another. This situation that may result, through either wind gusts or , in the creation of a hybrid of the two species.
We may thus suggest the following interpretation of the Yerushalmi. The sweetening of the olives by the host palm tree does not result from the grafting itself, but rather occurs due to the process of pollination made possible by the grafting. At times, a farmer may perform grafting for purposes of merging two species, and the merging occurs through the pollination that takes place as a byproduct of the grafting, which brought about the physical proximity between the two species. This pollination is the "sweetening" of which the Yerushalmi speaks.
For our purposes, the significant point is that this problem of pollination, which results in the emergence of a new species, does not arise in modern grafting techniques. Today, all branches of the host tree are removed before grafting. Only the tree's trunk remains, upon which the grafting is performed. This technique does not allow for the possibility of cross-pollination between the host tree and branch. Thus, the Yerushalmi's concern becomes entirely irrelevant in the context of modern grafting.
In his book "Eretz Chemda," Rav Shaul Yisraeli develops this approach, and on this basis he arrives at a novel conclusion. In his view, contemporary grafting, which, due to the removal of all the branches from the host tree, allows no chance for crossbreeding, is not, strictly speaking, forbidden. He argues that the Torah forbids only the type of grafting that corresponds to crossbreeding animals, namely, grafting that allows for the creation of a new species. Even if we do not accept this theory concerning the prohibition against grafting, we may still adopt Rav Yisraeli's general approach to grafting, namely, that it does not, in itself, involve the merging of two species. This merging occurs only incidentally, and under modern grafting conditions, it cannot occur at all.
According to this approach, it turns out that the Yerushalmi's comments do not contradict botanical science, and we may indeed assume that the tree has no effect on the grafted fruit's identity. Needless to say, once we accept this assumption, we should not disqualify an etrog ha-murkav on the basis of its identity. It is indeed an etrog, and may be used for the mitzva of arba minim.
We must, however, address another Talmudic source: Sota 43b. The Gemara there deals with the prohibition of orla (the consumption of fruit grown within the first three years of the tree's planting), and over the course of its discussion, the Gemara cites the following remark of Rabbi Abahu: "A young [tree] that one entangled with an adult [tree] – the young becomes nullified by the adult, and the law of orla does not apply." Rabbi Abahu, whose comments are not challenged throughout the Gemara's discussion, establishes that we determine the branch's identity for purposes of the orla prohibition based on the status of the host tree. In his view, the grafted branch loses its identity and takes on the identity of the older tree.
This halakha, that the branch becomes "nullified" by the host tree, effectively renders irrelevant the botanical fact that the branch remains genetically independent. According to Rabbi Abahu, after grafting, Halakha considers the tree a single, indivisible unit whose identity is determined by the host tree; the independent botanical identity of the branch is of no consequence. On the basis of this Gemara, the Alshikh (responsa, 210) concludes that we must disqualify an etrog ha-murkav. This conclusion is valid, as stated, even if we assume that the host tree does not affect that identity of the fruits grown on the grafted branch.
The Chatam Sofer (glosses on the Shulchan Arukh, O.C. 648, commenting on Magen Avraham 648:3) disagrees, claiming that we cannot apply Rabbi Abahu's ruling on orla to our issue of etrog ha-murkav. He writes:
"His comments are startling; of what relevance is the issue of the 'young' and the 'adult' to here? There we deal with the issue of the nullification of their issur [forbidden substance], not with the transformation of the fruit, such that an apple is made from a nut!"
The Chatam Sofer argues that the "bittul" (nullification) of the branch with respect to the tree occurs as a purely halakhic phenomenon applying only to the realm of "issur ve-heter" (mixtures of forbidden and permissible substances). This mishna addresses the possibility of nullifying the prohibited orla branch by virtue of its attachment to the older tree. This discussion has no relevance to the issue of the botanical identity of the fruits grown on a given branch. Rabbi Abahu's ruling thus has no impact upon the question of the identity of an etrog grown on a branch grafted onto a lemon tree.
We may perhaps draw support for the Chatam Sofer's position (that the "bittul" described by Rabbi Abahu is but an abstract halakhic concept that applies only to the presence or elimination of issur, and does not effect the definition of the actual item) from a passage in the Mishneh Le-melekh. In Hilkhot Me'ila (7:6, s.v. ve-ra'iti), the Mishneh Le-melekh comments on the possibility of punishment for partaking of a mixture of heter and issur (permissible and forbidden foods):
"I cannot understand his position, how bittul is relevant here. We hear of bittul only eliminating the issur and rendering it permissible for consumption. But if the majority [of the mixture] is issur, then although a prohibition still applies, we have not heard that we can hold one liable for lashes, karet or a sacrifice [for partaking of the mixture]!"
The Mishneh Le-melekh distinguishes here between eliminating issur in a mixture consisting mostly of heter, which Halakha recognizes, and the elimination of heter within a mixture in which issur constitutes the majority. This distinction is possible only to the extent to which we assume that the law of bittul applies only with regard to halakhic definition of mixtures, and to the presence of issur within a mixture. It has no bearing on the general definition of the mixture. Therefore, when a smaller quantity of issur mixes with a larger amount of heter, Halakha permits the mixture because the issur becomes nullified. When, however, a small amount of heter mixes with a majority of issur, then although the heter becomes nullified, it has not been turned into issur such that one would be liable for its consumption, since it has not lost its actual identity.
The Chatam Sofer bases his argument against the Alshikh on this very principle. The branch's bittul with respect to the tree does not change its identity; it affects only the branch's previous status of issur. It retains its original botanical identity, and an etrog ha-murkav thus remains an etrog.
Even should we accept the Alshikh's line of reasoning, by which Rabbi Abahu's ruling indeed applies as well to the status of an etrog ha-murkav, we need not necessarily disqualify an etrog ha-murkav. The Benei Efrayim maintains that, in truth, the Torah does not require specifically an etrog for the mitzva. Rather, one must take a fruit that meets all the criteria mentioned in the Gemara, which Chazal derived from Biblical verses. After all, the Torah never specifies an etrog. Instead, it describes the characteristics of the fruit which one must take on Sukkot, such as that it remains on its tree all year round, the tree has a similar taste to the fruits itself, and so on (see Sukka 35a). Once a fruit meets all these criteria, it qualifies for the mitzva of arba minim, even if we cannot call it an etrog.
This position, however, is far from simple, and appears to be subject to a debate among the Rishonim. The Rambam, in his introduction to his Commentary on the Mishna (s.v. ve-ka'asher met Yehoshua), claims that we have an oral tradition originating at Sinai that we must take specifically an etrog. When the Gemara searches for a textual source for the specific requirement of etrog in the Torah, it simply attempts to find some Biblical allusion to what we have already received via oral tradition. The Ramban, in his commentary to Chumash (Vayi23:40), explains similarly, that "etrog" is the Aramaic translation of the Hebrew word "hadar," with which the Torah describes the fruit taken on Sukkot. According to the Ramban, then, the Torah explicitly specifies that on Sukkot we take an etrog/hadar.
By contrast, Tosefot (Sukka 33a, s.v. ve-eima) imply that in their view, the Torah itself does not require one specific species, and a given species' qualification for the mitzva is determined based on the parameters extracted from the verses. Addressing the possibility raised by the Gemara of disqualifying an "Egyptian hadas" for use in the arba minim, Tosefot write,
"Why did the Gemara think to disqualify it due to its accompanying name ['Egyptian']? Does the verse mention 'hadas'? In fact, we would have allowed even using a 'hirdof,' if not for the fact that it says, 'Its ways are ways of pleasantness' [and a 'hirdof' has sharp, stinging leaves]."
Tosefot maintain that the Torah does not establish categorical requirements for specific species, and the validity or disqualification of a given species depends on their meeting the parameters mentioned in the Talmud. Thus, the possibility of permitting the use of etrog ha-murkav based on the view of the Benei Efrayim depends on this debate among the Rishonim.
The Chelkat Yoav deals with the Gemara in Sota differently. In his view, the branch indeed becomes "batel" with respect to the tree, as Rabbi Abahu posits, but we nevertheless consider the fruit an etrog. The only problem that arises involves the characteristic of "ta'am etzo u-piryo shaveh" – that the tree and fruit have a similar taste. At first glance, a grafted etrog fails to meet this prerequisite, given that the tree is a lemon tree, and its taste differs from that of an etrog. In truth, however, one may dismiss this problem by claiming that "ta'am etzo u-piryo shaveh" is intended not as a necessary characteristic, but rather as an indicator of the species required by the Torah. Indeed, the Ritva (Sukka 35a) writes, "Since the Torah wrote 'peri etz' and not just 'hadar,' which is the name of the etrog, this teaches that this [word] 'hadar' refers to the etrog, whose fruit and tree are similar." If the similarity in taste between the tree and fruit is merely an indicator of the species of etrog, we may then allow the use of an etrog that grows on a lemon tree. Needless to say, we would then have to assume that a fruit that grows on a grafted branch retains its original identity, and does not automatically take on the identity of the tree.
B. "MITZVA HA-BA'A BA-AVEIRA"
Irrespective of the issue of the identity of an etrog ha-murkav, we must address a separate problem, namely, the prohibition against grafting and the permissibility of using an etrog grown through the violation of this law.
Let us begin by examining the prohibition against grafting. The Torah never forbids grafting explicitly, but the Gemara (Kiddushin 39a) derives this prohibition from a parallel between grafting and crossbreeding animals:
"'You shall observe My statutes' – the statutes that I have already legislated for you; 'You shall not let your cattle mate with a different kind; you shall not sow your field' – just as regarding your cattle crossbreeding [is forbidden], so, too, regarding your field, grafting [is forbidden]."
The Gemara thus learns from this verse that grafting two species together violates the prohibition of kilayim. Consequently, one who wishes to use an etrog ha-murkav for the mitzva of arba minim appears to run into the problem of performing a mitzva through the violation of a prohibition. This problem divides into two distinct issues: "ma'us," using something repugnant for purposes of a mitzva; and "mitzva ha-ba'a ba-aveira" – one cannot fulfill a mitzva in a manner that entails a violation.
We will first address the issue of mitzva ha-ba'a ba-aveira. Towards the beginning of the third chapter of Masekhet Sukka, the Gemara applies this principle to the mitzva of lulav. As a source for this rule, the Gemara cites a verse in Sefer Malakhi dealing with the offering of a stolen sacrifice, but the Gemara extends it to the arba minim as well. The Levush (cited by the Taz, O.C. 649:3) raises this issue in the context of an etrog ha-murkav:
"I claim that they are disqualified according to Torah law, for it is known that they were grafted, that a branch from the etrog tree was grafted onto a… lemon tree, or vice versa, and so the transgression of grafting has been violated with it. Even if gentiles grafted it, one view… maintains that even a gentile is commanded with regard to grafting trees. Once a transgression has been violated with it, then even though it is permissible for consumption, it is repugnant for God."
The Levush applies the disqualification of etrog ha-murkav even when gentiles performed the grafting. He bases his position on the Gemara in Sanhedrin, which claims that grafting is forbidden even for gentiles. The Rambam indeed codifies this ruling: "According to oral tradition, gentiles are forbidden only from crossbreeding animals and grafting trees" (Hilkhot Melakhim 10:6).
The Taz, however, disputes this position, based on Rav Huna's instruction to hadasim merchants, cited towards the beginning of the third chapter of Sukka (30a): "When you purchase hadasim from idolaters, you should not cut them. Rather, they should cut them and give them to you. Why? Most idolaters steal land." The Taz understood Rav Huna's instruction as intended to prevent the problem of mitzva ha-ba'a ba-aveira, by having the gentile perform the act of theft (cutting the hadasim from the ground). On this basis, the Taz concludes that if another person commits the sinful act, then even if that person is himself forbidden from performing that act (just as gentiles are included in the prohibition against theft), the mitzva ha-ba'a ba-aveira rule does not apply.
However, this argument of the Taz appears to oppose the view of Tosefot (Sukka 30a, s.v. mishum), who ask why the Gemara does not disqualify a lulav taken from the idolatrous "asheira" tree due to mitzva ha-ba'a ba-aveira. This question obviously assumes that even when someone else commits the given transgression, the problem of mitzva ha-ba'a ba-aveira arises – in direct opposition to the theory advanced by the Taz.
We may, however, resolve the position of the Taz with that of Tosefot, by drawing a distinction between theft and idol worship, a distinction suggested in Responsa Nefesh Chaya (2). The Nefesh Chaya claims that unlike theft, which brings about no essential change in the object, pagan worship transforms the fundamental status of the item worshipped. Therefore, when it comes to theft, we would not apply mitzva ha-ba'a ba-aveira to disqualify as object stolen by a gentile, as the Taz claimed, based on Rav Huna's instructions to the merchants. An asheira tree, however, has the status of an object of issur, and therefore the halakha of mitzva ha-ba'a ba-aveira disqualifies it under all circumstances, even when somebody else committed the violation, as Tosefot indicate.
If we would assess the status of an etrog ha-murkav in light of this distinction, then even if we do not define it as an "object of issur" as we would an asheira tree, we must still render it forbidden even if a gentile performed the grafting. After all, this etrog came into existence through the act of grafting, and according to Tosefot (ibid.), the law of mitzva ha-ba'a ba-aveira disqualifies a given object for mitzva use only when the mitzva's fulfillment cannot occur without a preceding violation. It turns out, then, that we may not fulfill the mitzva of arba minim with an etrog ha-murkav, due to the problem of mitzva ha-ba'a ba-aveira.
As mentioned, we must deal as well with the issue of "ma'us," using an object considered repugnant for the observance of a mitzva. The Gemara (Avoda Zara 47a) cites the following question posed by Reish Lakish concerning this matter: "If one bows to a palm tree – may its lulav be used for the mitzva? … Is it repugnant with respect to God, or not?" Reish Lakish works off basic assumption that there exists a halakha of "ma'us" with regard to sacrifices, and it extends beyond the parameters of the rule of mitzva ha-ba'a ba-aveira. He is uncertain as to whether or not this law applies to mitzvot, as well. The sugya there does not reach a definitive conclusion, but we do find such a conclusion in the Yerushalmi (Kilayim 1:2):
"Rabbi Shimon Ben Lakish asked: May one bring a lulav from it [a palm that had been worshipped]? Are mitzvot like sacred property [sacrifices], or are they not like sacred property? If you claim that they are like sacred property, then he may not bring; if you claim that they are not like sacred property, then he may bring. Obviously, he may bring from it a lulav, for a mitzva is not like sacred property."
In addition to this ruling of the Yerushalmi, there appears to be a definitive ruling on this matter in the Talmud Bavli, as well, at least on the level of "di-eved" (after the fact). Rava comments (Sukka 31b), "One should not take a lulav of avoda zara, but if he took, it is valid." We may view this ruling of Rava as the Bavli's conclusion on this issue, particularly if we adopt the position of Tosefot (Avoda Zara 47a, s.v. mi) that Reish Lakish agrees with Rava that such a lulav may be used, "be-di'eved," even before the tree's divine stature has been renounced ("bittul"). Reish Lakish questions only whether one may use a lulav from a tree of idolatry "le-khatechila" (optimally) after the tree's divine stature has been renounced.
It turns out, then, that the problem of "ma'us" would not disqualify the etrog; according to Rava, it should not be used "le-khatechila," and according to the Yerushalmi, one may use this etrog for the mitzva even "le-khatechila."
In any event, the issue of the transgression having been violated in the context of an etrog ha-murkav is very limited in scope, in comparison with the problem of the etrog's identity, discussed in the first section of the shiur. With regard to the prohibition against grafting, the Rambam writes (Hilkhot Kilayim 1:7):
"One who sows seeds of kilayim, and also one who grafts trees of kilayim – although he is liable for lashes, they are permitted for consumption… One may plant a shoot from a tree that had been grafted with kilayim and sow from a vegetable seed that had been planted with kilayim."
This means that the prohibition of grafting applies only to the tree upon which the grafting actually occurred; one is permitted to plant additional trees from seeds extracted from the grafted tree. Consequently, the problems of "ma'us" and mitzva ha-ba'a ba-aveira arise only when dealing with the etrogim that grew on the very tree upon which the grafting was performed. All etrogim grown on trees upon which no grafting has taken place are suitable for the mitzva, regardless of the source of these trees. Needless to say, however, this ruling of the Rambam will not resolve the first issue addressed in the shiur – the problem of the species' identity. Assuming the latter problem indeed exists, it applies to all etrogim originating from the grafted branch, even generations later.
Two basic problems arise concerning the suitability of an etrog ha-murkav for the mitzva of arba minim on Sukkot. One problem involves the transgression committed when grafting a tree. In light of the Yerushalmi's ruling, as well as Rava's conclusion regarding an etrog used for idolatry (a conclusion accepted as halakha), it would appear that the problem of "ma'us" does not apply to an etrog ha-murkav. There does, however, exist the problem of mitzva ha-ba'a aveira, but this issue concerns only etrogim grown on the tree upon which the grafting was performed, not those taken from trees originating from the grafted tree.
The second issue is the identity of the species of an etrog ha-murkav. This issue poses a more significant problem, since once we consider an etrog ha-murkav a different species than the etrog, then etrogim grown on all trees resulting from the initial grafting, regardless of how far in the distant past it occurred, would be disqualified. However, we know without a doubt from botanical science that the host tree has no effect on a fruit grown on the grafted branch. We tried to show how this scientific fact does not contradict the comments of the Yerushalmi in Kilayim or of the Bavli in Sota.
We should add that nowadays, we have no way of knowing with certainty that any given tree does not originate from a grafted etrog, and assumptions made about certain orchards that they stem from pure etrog trees are based merely on speculation and are far from certain.
 Book 2, vol. 2, 3. See especially paragraphs 7-11.
 If we accept Rav Yisraeli's position, that the prohibition of grafting does not apply to contemporary grafting, then the problem of mitzva ha-ba'a ba-aveira, which we will address in the second half of the shiur, is automatically resolved.
 However, the Nefesh Chaya (2, s.v. ve-hinei kevar heiveiti) claims that even in such a case, the taste of the tree and fruit are, in fact, similar. The fact that the etrog grew on a branch taken from an authentic etrog tree suffices for us to consider the taste of the tree equivalent to the taste of the fruit.
 The Shakh (Y.D. 297:3) overlooked this ruling of the Rambam and determined that gentiles are included only in the Seven Noachide Laws, and the prohibitions of crossbreeding and grafting do not apply to them. This observation is made by Rabbi Akiva Eiger (in his "tosefot" to the Shulchan Arukh).
 The "Kapot Temarim" (Sukka 31b, s.v. ve-kasheh li) raises a difficulty concerning this Gemara. Later in the Gemara's discussion, Rav Papa asks whether one may make tzitzit from wool taken from an animal used for idolatry. The Rambam and Shulchan Arukh rule that this wool may not be used for tzitzit. The question arises: Why would we disqualify this wool for use as tzitzit but allow the use of a lulav taken from an asheira tree? The Chelkat Yoav (32:1, s.v. ve-ha-nireh le-aniyut da'ati) answers that tzitzit must be spun "lishmah," with specific intent for the mitzva, and it therefore has the status of a "cheftza shel mitzva" (mitzva object). A lulav, by contrast, is considered merely a "tashmish shel mitzva," an object that serves a purpose in the fulfillment of a mitzva, rather than a mitzva object itself. Clearly, there is room to question the rationale underlying this explanation. Comprehensive treatment of this issue lies beyond the scope of this shiur.
 The exception to this rule is the Yemenite etrogim, which, reputedly, are known to have originated from authentic etrog trees.