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  • Rav Moshe Taragin



Lecture #05: Kilayim

By Rav Moshe Taragin



Three different prohibitions govern the practice of mixed planting.  Trees may not be grafted or otherwise combined and grains cannot be mixed when sown.  In each of these two instances, the produce is permissible to eat even though the actual act of planting is prohibited; hence the allowance to eat fruits from grafted trees.  Only the third form of kilayim, the prohibition of kila'ei ha-kerem, mixing other seeds with grape seeds, yields a prohibition upon the resultant produce.  Only kila'ei ha-kerem are "assur be-hana'a," prohibited to eat or to derive any other form of benefit from.  The source of this prohibition is found in Devarim 22:9, which warns against planting seeds "pen tikdash ha-milea'ah," lest the resulting produce become "kodesh," which the gemara interprets as a reference to its being forbidden. 


In describing the forbidden produce, the pasuk includes two different references – "pen tikdash ha-mile'ah ha-zera asher tizra."  It describes the seeds (zera) as prohibited, suggesting that the prohibition develops only if the seeds and grapes were PLANTED together.  However, the pasuk also describes GROWTH (ha-melei'ah), which implies that as long as the two seed types grew together an issur obtains.  In several locations (see Pesachim 25a), the gemara infers two separate scenarios of issur. If the seeds were originally planted TOGETHER, the produce is immediately forbidden; if they were planted separately (e.g., divided by a wall) and then allowed to grow together (after the wall fell) they become forbidden only if they grew mixed together long enough that they increase in size. In this latter scenario, the mixed plant is considered kilayim once the joint growth of the plants equals 1/200 of their size before the mixture took place. 


This shiur will address the second scenario of joint growth and how this rule is to be understood. Why should less than 1/200th growth be permissible but more than that fraction create a prohibition? 


Rabbenu Tam assumed that this fraction reflects classic ta'arovet principles.  Typically, forbidden material, when mixed with permissible food, yields an issur upon the entire mixture if it comprises up more than 1/60th of the mixture.  Some more severely prohibited foods impose a prohibition even in proportions less than 1/60th.  For example, teruma can prohibit a mixture in quantities of 1/100th.  Rabbenu Tam assumes that kilayim – which is more severe than teruma - creates an issur in a mixture when it is found in a quantity of 1/200th of the total crop.  Until the joint growth reaches a proportion of 1/200th (for example, if it only grows 1/400th of the original), the prohibited produce is nullified by the permissible produce which existed before the mixture took place.  However, once the prohibited part of the crop reaches the magic number 1/200th, it cannot be cancelled by the permissible quantity and a prohibition emerges for the entire mixture. 


Based upon this view, classic ta'arovet principles should apply to the 1/200th rule of kila'ei ha-kerem. In classic ta'arovet protocol, we apply the rule of kama kama batel, which prevents independent insufficient quantities of issur from combining to form a sufficient quantity.  For example, if issur fell into a ta'arovet in the proportion of 1/120th and on the following day another 1/120th fell in, the two quantities do not form the combined 1/60th necessary to create issur.  Each insufficient quantity is respectively annulled through the rule of kama kama batel. Accordingly, Rabbenu Tam asserted that if the 1/200th accumulation of kila'ei ha-kerem is interrupted, the quantities cannot combine toward the 1/200th proportion.  For example, if the wall separating grapes and other seeds fell and the two grew jointly an amount 1/400th of the original size, after which the wall was rebuilt and fell again, allowing a second growth of 1/400th, the produce is not forbidden.  Even though the joint growth exceeds 1/200th, since the growths accumulated separately, they do not combine. Only if the quantities of joint growth occur without interruption can they form a total quantity of 1/200th and be considered kilayim. 


The Ramban disagreed with Rabbenu Tam, arguing that classic ta'arovet models do not apply to kilayim growth.  Firstly, laws of bitul may not apply to growing produce.  Typically, the laws of bitul pertain to items that loose their identity in mixture.  Growing produce may retain their autonomous status, and the concept of bitul may therefore not be applicable (see Nedarim 58).  Additionally, the Ramban questions the applicability of bitul models to kilayim because, in this case, there is no actual encounter between issur and heter.  The original plant is permissible and the jointly grown produce is also permissible – until it reaches the proportion of 1/200th.   The concept of bitul only applies when one of the items in the mixture is forbidden and is nullified by the permitted matter.  We can not say that growth of less than 1/200 is nullified by previous growth because at that point the growth is still permissible and the rules of bitul do not apply. Accordingly, even less than 1/200th should create a prohibition; even 1/400th of the original growth is kilayim and it should not become bateil to the original matter since an encounter between two permissible items cannot create issur. 


The Ramban in his comments to Bava Batra (2a), suggests a very different model.  Until the grapes and seeds have grown to 1/200th of their original growth, they cannot be considered as having grown JOINTLY.  Once they have grown and increased by that proportion, there are considered mixed fruits, and therefore prohibited kilayim.  Rabbenu Tam viewed the proportion as a CONTEST of prohibited matter vying with, and ultimately outweighing, original permitted matter; the Ramban viewed the proportion as merely determining a point of full union after which the ENTIRE ITEM achieves a status of kilayim, rendering a comprehensive issur. 


Although there are numerous nafka minot to this question, we will mention three initial issues.  First and most obviously, the Ramban disagrees with the Rabbenu Tam's theory regarding interrupted accumulation.  According to Rabbenu Tam, two distinct fractions of interrupted growth cannot combine to form the requisite 1/200th quantity.  By contrast, the Ramban ruled that such accumulation would yield an issur.  If the joint growth initially accumulated by 1/400 and subsequently a wall was built and felled, a secondary growth of 1/400 can combine to achieve full 1/200th growth and the prohibition of kilayim. As ta'arovet models do not apply, the minimal quantities do not cede their status.  Ultimately, any combined growth of 1/200th indicates joint growth, rendering the entire produce kilayim. 


A second difference involves the method of gauging the 1/200th fraction.  Although the gemara makes no mention of how to measure the growth, an ambiguous statement in the Yerushalmi leads to a fascinating machloket between the Rambam and Ra'avad (Kilayim 5:21).  The Ra'avad adopts the more logical method:  A specific quantity of the produce is detached and immediately weighed.  If weighed x amount of time later, we can determine a ratio of "y" weight/ "x" time; Namely we can determine that over "x" time it lost "y" weight.  The Ra'avad further assumes that this ratio dictates weight loss after harvest AS WELL AS weight gain during growth.  For example, if the plant decreases 1/800th of its weight in 30 minutes, it can be said to grow that same amount in 30 minutes.  As such, if the grapes and seeds grew together for 2 hours, they grew 1/200th (4x 1/800) and are forbidden.  This procedure allows us to determine the necessary time for joint growth- and ultimately kalayim.


The Rambam suggests a different method for determining this growth.  Produce is harvested and the time it takes to shrivel – to lose all its moisture and die - is measured.  This time reflects its "lifespan" in time "x."  If the grapes and seeds grew jointly 1/200th of this lifespan, they are prohibited.  For example, if the produce desiccates entirely in 100 hours, then 1/200th of its lifespan would be 30 minutes.  If the grapes and seeds jointly grew this amount of time, the prohibition of kilayim develops.  Unlike the Ra'avad, who gauged the prohibition by weight, the Rambam measured pure time. 


Perhaps theses different methods of gauging growth reflect different views of the dynamic of the issur.  The Ra'avad saw 1/200th as the point at which new MATTER outweighed old MATTER and imposed a prohibition.  Since he agreed with Rabbenu Tam's thesis, he attempted to gauge the relative weight of the new growth compared to its original weight.  By contrast, the Rambam may have agreed with the Ramban.  Kilayim is not a contest of original permissible produce against new forbidden produce.  Instead, we assess whether they have grown together, at which point the entire crop is rendered kilayim.  Gauging this question of whether they have grown together can best be accomplished through measuring how long they have grown when compared to overall lifespan.  Hence, the Rambam chose time as the gauge, whereas the Ra'avad chose weight. 


Finally, the Rabenu Tam and the Ramban may disagree regarding a situation in which only one of the items accrued 1/200th growth .  For example, if the vegetables grew more than 1/200th and the grapes did not, do we prohibit the grapes as well?  Without question, the Rabbenu Tam would not envision a prohibition upon the grapes.  The new matter which has grown is the only item that is prohibited.  Once that new matter reaches 1/200th, the entire item becomes mixed with issur and prohibited.  If the grapes did not grow this amount, there is no reason they should become prohibited based upon 1/200th growth in the vegetable. 


According to the Ramban, however, if only one of the items grew sufficiently it may indicate sufficient joint growth to create an overall status of kilayim.  Perhaps 1/200th growth in one item can cause kilayim status and prohibition in both crops.  In fact, some infer this from the Rambam (ibid), further suggesting that the Rambam adopted the Ramban's position about kilayim and not Rabbenu Tam's.