Kil'ayim (prohibition)

Torah law forbids the wearing of Kil'ayim (shatnez) – sheep wool and linen fabrics that have been hackled together, or spun and woven together. Likewise, "intertying" sheep wool and linen together is forbidden, the two exceptions being garments of kohanim worn in the Temple and tzitzit. Concerning tzitzit, the Sages of Israel permit using wool and linen strings in tandem only when genuine blue dye tchelet is available, whereas kabbalist sources go a step further by encouraging this practice.[2] The Torah forbids only wool and linen to be worn together.[3] Camel's wool, Cashmere wool, Yak fiber, and the like of such fibres, are not prohibited to be worn with linen.[4]

According to Maimonides, if a Jew had purchased an all-woolen product from a gentile and wanted to ascertain whether or not it was, indeed, pure wool – without the admixture of flax-linen, its fabric could be tested by dyeing. A dye-solution applied to the fabric would reveal whether or not it was of pure wool, as wool and linen products do not retain the same shades in a dye solution.[5]

The prohibition of sowing together diverse seedlings is derived from the biblical verse, "You shall not sow your field with two kinds of seed" (Leviticus 19:19), and which prohibition has been explained to mean planting or sowing two or more diverse vegetable crops within a radius of three-handbreadths, ca. 27 centimetres (11 in), from one another, where they draw nutrients from each other.[6] As a first resort, however, one is to distance two or more diverse vegetable crops from each other at a remove of six-handbreadths, ca. 54 centimetres (21 in), even if their foliage were to grow and intermix.[7][8] Two or more diverse seed-crops must be distanced enough so as to be distinguished from each other as two separate plantings.[9] The laws governing diverse seed-plantings or vegetables apply only to crops grown in the Land of Israel, but do not apply to seed-crops or vegetables planted outside the Land of Israel.[6][10]

According to biblical exegete Nachmanides, the reason for its prohibition being that when seedlings draw nutrients from other seedlings, their properties and natural forms are changed thereby and the sower cancels thereby the fixed design and purpose of the universe.[11]

Diverse seed-plantings or vegetables that grew together in violation of the biblical command are permitted to be eaten,[12] although the crop itself must be uprooted.[13][6][14] If two diverse grain seeds (e.g. wheat and barley) were inadvertently mixed together, they must be separated before they can be sown. If, however, there were 24 parts more of one grain than the other (ratio of 24 to 1), the lesser grain is considered cancelled by the other, and may still be sown together.[6] If there were not 24 parts more than the mixed grain, the whole must be sorted.[15]

The Mishnah (Kil'ayim 1:1) explicitly permits faba beans (Vicia faba) (Hebrew: פול) and mung beans (Vigna radiata; Vigna mungo) (Hebrew: ספיר)[16] to be planted together. It also permits the planting of White mustard (Sinapis alba) (Hebrew: חרדל) and of Egyptian mustard (Brassica nigra) (Hebrew: חרדל מצרי) together (Kil'ayim 1:2), despite being two different genera.[17][18] However, White mustard (Sinapis alba) (Hebrew: חרדל) and Charlock mustard (Sinapis arvensis) (Hebrew: לפסן), though also similar in appearance, may not be planted together (ibid. 1:5).[19]

Field showing distinct plots for different species

Cucumbers (Hebrew: קשות) and muskmelons (Hebrew: מלפפון),[20] although two different species, are not considered "diverse kinds" with respect to each other and may be planted together.[21] Rabbi Yehudah, disputing, says that they are considered "diverse kinds" with respect to each other and cannot be planted together.

Although two different species, the Mishnah (Kil'ayim 1:3) permits planting together turnips (Brassica rapa subsp. rapa) (Hebrew: לפת) with rape (Brassica napus) (Hebrew: נפוס).[22] Likewise, cauliflower (Brassica oleracea botrytis) (Hebrew: תרובתור) and kohlrabi (Brassica var. caulorapa) (Hebrew: כרוב), although different species, are permitted to be planted together.[23] Maimonides, in his commentary on the same Mishnah, explained the word karūb as having the Judeo-Arabic connotation of כרנב, meaning either cabbage (Brassica oleracea) or kale (Brassica oleracea var. acephala).[24]

Grafting of two varieties of citrus trees

The prohibition of grafting of trees is treated on in the Mishnah (Kil'ayim 1:4).[25] Among trees, while it is permissible to grow two different kinds of trees in close proximity to each other, it is forbidden for an Israelite (or a gentile working on behalf of an Israelite) to graft the branch (scion) of one tree onto the stump of another tree to produce thereby a hybrid fruit if the trees are not one and the same kind. Quinces (Cydonia oblonga) (Hebrew: פרישין) are named as an exception, for if a branch taken from it were grafted onto a stump belonging to hawthorns (Crataegus azarolus) (Hebrew: עוזררין), although they are two different species, it is permitted unto Israel to benefit therefrom, since they are considered related.[26][27] Likewise, to graft the branch of Krustemelin (said to be the "Calaprice pears")[28] onto the rootstock of an ordinary pear (Pyrus communis) is permitted. However, apple trees (Malus domestica) (Hebrew: תפוח) grafted onto medlars (Mespilus germanica) (Hebrew: חֻזרַד),[29] or peach trees (Prunus persica) (Hebrew: פרסקין) grafted onto almond trees (Prunus dulcis) (Hebrew: שקדים), or jujubes (Ziziphus jujuba) (Hebrew: שזפין) grafted onto Christ's thorn jujubes (Ziziphus spina-christi) (Hebrew: רימין), although similar in appearance, are "diverse kinds."[30][31] The fruit produced by grafting the bud of one dissimilar tree onto the rootstock of the other are permitted to be consumed by Israel,[32][33][34][6] although the trees themselves, according to some authorities, are not permitted to be maintained.[35][36]

The Chazon-Ish, who was uncertain about the identity of the trees mentioned in the Mishnah owing to conflicting opinions, made it a rule to be stringent in all of them, prohibiting their grafting in all cases. A Jew who transgressed by grafting two dissimilar trees was, formerly, liable to flogging.[37] The prohibition of grafting two dissimilar trees applies to trees in the Land of Israel, as well as to trees outside the land of Israel; whether trees belonging to a Jew or to a gentile.[38]

The Sages of Israel have described the prohibition of growing diverse kinds in a vineyard, strictly from a biblical perspective, as referring only to two grain varieties (such as wheat and barley), or either to hemp and arum, or similar plants which reach maturity with the grain.[39][40][41] By a rabbinic prohibition, however, it is not permitted to plant or maintain a vineyard while the vineyard shares the same immediate ground with any vegetable or seed-crop grown for food (e.g. mustard seeds, chickpeas, etc.).[39] The result of doing so would be to cause its owner to forfeit the seed-crop together with the increase of the vineyard thereof.[42] Therefore, the rabbis made it incumbent upon husbandmen and vine-dressers to distance their seed-crop from a vineyard. According to Maimonides, if a trellised vine of at least five plantings was made alongside a fence or a wall, even if the stumps of the grape-vines were distant from the wall one cubit, the planter of seed is only permitted to sow seed 4 cubits beyond the wall or fence, since the grape-vine is prone to spread itself as far as the wall, and there must always be at least 4 cubits from a vineyard and the seed-crop.[43] Certain plants that grow of themselves in a vineyard, such as lianas (Cissus spp.),[44] bindweed (Convolvulus spp.),[45] Sweet clover (Melilotus), and the anemone (Anemone coronaria), do not account as "diverse kinds" to cause its owner to forfeit the crop of the vineyard altogether.[46] Had a person transgressed and grew a seed-crop within his vineyard, not only is the produce forbidden to be eaten, but also had he sold the produce, the proceeds accruing from the sale of such produce are also forbidden.[47][3]

Vineyard growing in Israel

If thorn bushes, such as camelthorn (Alhagi maurorum) (Hebrew: ההגין), and box-thorn (Lycium shawii) (Hebrew: אטדין), grew within a vineyard, they are not accounted as a seed-crop and may be sustained in a vineyard, the rabbis giving to them the classification of trees amongst trees.[48] However, in places where thorn bushes are used as fodder for camels and the owner of the vineyard is content to have the thorn bushes grow in his vineyard to that end, the thorns bushes, if maintained, would render the entire vineyard forbidden.[49]

By a rabbinic injunction, the prohibition of growing diverse seed-crops in a vineyard extends to vineyards vintaged by Jews outside the Land of Israel.[50] The planter transgresses the biblical command from the moment grain begins to take root within a vineyard, and the grapes have reached the size of white peas (Vigna unguiculata).[51][52][53]

In modern classification of animals, the genus Canis is used to include dogs, wolves, coyotes, and jackals. Even so, the mating of dogs and wolves is forbidden. Similarly, the mating of a horse and mule (even though they cannot reproduce) is forbidden.[54]

Though a Jew is forbidden to crossbreed a horse and a donkey (producing a hinny or mule), had a gentile bred them, it is permitted for a Jew to make use of them.