Peninei Halakha

05- Sha’atnez

01. The Mitzva

The Torah commands us not to wear a garment made of wool and linen, as it states: “You shall observe My statutes: you shall not mate your animal with a different species, you shall not sow your field with two kinds of seed, and a garment of mixed kinds, sha’atnez, shall not come upon you” (Vayikra 19:19). It also states: “You shall not wear sha’atnez, wool and linen together” (Devarim 22:11).

The wool included in this prohibition is sheep’s wool. Male sheep are called rams, and females are called ewes. The fleece of other animals is not included, because it is not called simply “wool” but is identified by a qualifying term. Thus, the prohibition does not apply to camel wool, goat wool (such as cashmere), rabbit wool (such as angora), or alpaca wool. In practice, from antiquity to the present, most of the world’s wool has come from sheep, which naturally produce abundant, high-quality fleece and are readily domesticated.

Flax is a plant with a single long stalk containing fibers that can be made into strong thread. With special processing, these fibers can be spun into fine thread and woven into attractive white garments. The prohibition of sha’atnez applies specifically to flax and not to fibers derived from other plants, such as hemp or cotton. In earlier times, most clothing was made of wool or linen; some therefore maintain that when the Torah uses the word “garment” without qualification, it refers to a garment made of wool or linen (Menaḥot 39b).

The prohibition of sha’atnez applies to wearing a garment containing both wool and linen. It does not prohibit wearing two separate garments, one made of wool and the other of linen. One may therefore wear wool pants with a linen shirt, or a wool robe fastened with a linen belt. As long as the wool and linen garments are not joined by sewing or a permanent knot, there is no prohibition (below, 6).

The prohibition applies to wearing garments containing wool and linen, not to making sha’atnez fabric for other purposes. It may therefore be used as a decorative wall hanging, as a parokhet for an ark, or to make a cloth purse or tent. It may also be used for burial shrouds, since the deceased are exempt from mitzvot. Likewise, one may manufacture sha’atnez garments for non-Jews, provided there is no concern that they will come into the possession of a Jew who might mistakenly wear them.

02. The Prohibition of Wearing and Draping

Clothing is intended to protect the body from cold, heat, and rain, and to provide adornment, dignity, and modesty. One who wears a sha’atnez garment for any of these purposes violates the prohibition, as the Torah states: “You shall not wear sha’atnez” (Devarim 22:11). The prohibition applies to shirts, pants, dresses, skirts, undergarments, socks, hats, cloth shoes, gloves, ties, decorative ribbons, and all other garments ordinarily worn. Even if only the garment’s hanging loop or attached label is sha’atnez, the garment may not be worn (SA YD 301:15).

The prohibition also applies when sha’atnez fabric is draped over the body for warmth, protection from heat, or modesty, even though it is not worn in the usual manner of a garment. The Torah states: “A garment of mixed kinds, sha’atnez, shall not come upon you” (Vayikra 19:19). Thus, any use of sha’atnez that provides a benefit ordinarily associated with clothing is prohibited. One may not cover oneself with a sha’atnez blanket or dry oneself with a sha’atnez towel, since both provide warmth. The Sages also prohibited using sha’atnez as a tablecloth, out of concern that someone might occasionally pull it over their legs for warmth (SA YD 301:9). For the same reason, they prohibited hanging a sha’atnez curtain, since adults or children might use it for warmth. It may, however, be hung above head height or made of stiff fabric, since it cannot then be used for warmth (ibid. 11). Nor may one use sha’atnez fabric to handle a hot pot or frozen object, since it protects the hand from heat or cold and thus provides a benefit ordinarily associated with clothing (ibid. 12).

One may, however, benefit from sha’atnez fabric in ways unrelated to clothing. Thus, it may be used for a tent or umbrella.

Moreover, according to many authorities, one may wear a sha’atnez garment when doing so serves a purpose entirely unrelated to clothing. Thus, if customs duty is imposed only on garments packed in luggage, a Jew transporting sha’atnez garments belonging to non-Jews may wear them over his clothes while crossing the border, provided he does not intend to benefit from them as clothing. Likewise, a clothing seller may put on a garment solely to display it to customers, provided he does not intend to derive any benefit from wearing it (Rosh; Ramban; Ran; Rema YD 301:6; Yam Shel Shlomo). Other authorities are stringent and prohibit wearing sha’atnez even for these purposes, whether to avoid customs duty or to display a garment to customers (Rambam, as understood by Beit Yosef; SA YD 301:5–6).[1]

[1]. The words “shall not come upon you” teach that sha’atnez is prohibited even when it is not worn in the ordinary manner. From the words “you shall not wear,” however, the Sages derived that the prohibition applies only when the fabric provides a benefit ordinarily associated with clothing (Yevamot 4b; Yerushalmi, Kilayim 9:1). Such benefits include warming the body and protecting it from the sun, rain, or dirt (Mishna, Kilayim 9:4; Meiri, Yevamot 4b), as well as adornment, dignity, and modesty (Ritva, Shabbat 29b; Pesaḥim 26b).

Some have suggested that the authorities disagree as to whether adornment and modesty are independently considered benefits of clothing (see Ha-sha’atnez Le-halakha 4:2–4). In fact, there is no substantive disagreement, since a garment worn for adornment or modesty is generally also capable of providing warmth. The more precise definition of a garment, then, is an item capable of warming the body, even if it is worn primarily, or even exclusively, for adornment or modesty. A tie, for example, is worn for appearance but can still provide some warmth. Similarly, a woman may wear a base-layer shirt solely for modesty, but it is nevertheless considered a garment because it can provide warmth. By contrast, a sha’atnez pendant designed solely as an ornament is not considered a garment and may be worn on a chain.

The Mishna states: “One may not wear kilayim, even over ten garments, even to ‘evade’ customs duty” – that is, to qualify legally for an exemption from the tax, as explained above (Mishna, Kilayim 9:2). Later, the Mishna states: “Clothing merchants may sell in their ordinary manner,” meaning that they may model the garments on their bodies, “provided they do not intend to protect themselves from the sun in hot weather or from the rain in wet weather; the scrupulous carry the garments on a pole” (Mishna, Kilayim 9:5). Rosh and the authorities who follow his view understand these two rulings to disagree, and they rule in accordance with the latter: one may wear a garment in the ordinary manner when the sole purpose is to display it, provided one does not intend to benefit from wearing it. The same reasoning permits wearing a garment to avoid customs duty, although the scrupulous refrain from doing so. This is also the view of Yere’im, Or Zaru’a, Ramban, Ran, R. Yeruḥam, and Semag. This is not considered a case of pesik reisha, in which the prohibited benefit is inevitable, because the wearer may derive no benefit from the garment at all, as when he is already sufficiently warm. Ran further maintains that when the prohibition itself is against deriving benefit, intent to benefit is a necessary condition. The act therefore remains permitted even if some benefit is inevitable.

Rambam, by contrast, rules in accordance with both passages, indicating that he does not understand them to disagree. In his view, clothing merchants were permitted to drape garments over themselves only in a manner unlike ordinary dress, such as without putting their arms through the sleeves. Since the garment is not worn normally, the absence of intent to benefit makes the act permissible. Wearing it in the ordinary manner, however, is always prohibited (R. Avraham b. Rambam; Mahari Kurkus; Beit Yosef; among others). Other authorities understand Rambam differently. In their view, a merchant may put on a suit in the ordinary manner in order to model it, since his sole interest is in displaying the garment and he derives no benefit from wearing it. A person seeking to avoid customs duty, however, specifically needs to wear the garment in order to obtain the exemption. Although his ultimate purpose is to avoid the tax, that purpose is achieved through wearing the garment itself (Taz; Shakh).

Some maintain that one may try on a sha’atnez garment to determine whether it fits, intending to buy it and then have the sha’atnez removed, since trying it on is not intended to provide the benefits of clothing (Riaz, cited in Shiltei Giborim, following Rosh and most Rishonim). Others prohibit this because the person intends to wear the garment as part of trying it on (Ḥokhmat Adam 106:20). When a garment merely might contain sha’atnez, one may try it on and then send it for testing (Yabi’a Omer 6:27; Ḥeshev ha-Efod 1:137; see also Ha-sha’atnez Le-halakha 4:26).

03. Sitting or Lying on Sha’atnez

By Torah law, one may sit or lie on sha’atnez fabric, even though it provides warmth. The Torah prohibition applies only when the sha’atnez is above or alongside the body in the manner of clothing, not when it is beneath the body, as the verse states: “A garment of mixed kinds, sha’atnez, shall not come upon you” (Vayikra 19:19). The Sages, however, prohibited sitting or lying on sha’atnez fabric, lest a loose thread wind around one’s skin or one mistakenly use the fabric as a covering. To prevent such errors, they extended the prohibition even when the sha’atnez is covered by ten layers of permitted fabric (Beitza 14b; SA YD 301:1).

If the sha’atnez fabric is too stiff to be used as clothing and lies on a firm floor or chair into which the person does not sink, however, the Sages did not prohibit sitting or lying on it. A layer must separate the fabric from the body, so that any loose thread cannot wind around the skin (SA YD 301:1). One may therefore lie on a stiff sha’atnez rug when another fabric is spread over it, or sit on a chair upholstered with sha’atnez when pants or a dress separate the body from the chair. Even if the upholstery itself is soft, it is treated as stiff fabric as long as it is stretched taut over the chair with nails or glue (Panim Me’irot 2:113).[2]

[2]. The Sages prohibited sitting or lying on sha’atnez fabric, lest a loose thread wind around one’s skin. They extended this decree even to a case in which ten layers of bedding separate the person from the sha’atnez (Beitza 14b). Some maintain that this extension applies only to fabric commonly used for clothing. If the fabric is not ordinarily worn, one may lie on it as long as it is covered (Rid; Riaz; Ran; Maharshal). Most authorities, however, maintain that the decree applies even to fabric not ordinarily used for clothing (Rashi; Rambam; Meiri; Sefer ha-Ḥinukh; Rosh; SA YD 301:1; Levush; Baḥ).

If the sha’atnez fabric is stiff, however, one may sit on it (Beitza 14b). According to most authorities, it must also be covered, so that no loose thread can reach the skin and wind around it (Rambam; R. Shimshon of Sens; SA YD 301:1; Shakh YD 301:4; and others). Some permit sitting on stiff fabric even without an intervening layer (Rid; Riaz; Ritva), while others permit this only when the fabric is extremely stiff, like a donkey’s saddlecloth (Rosh; R. Yeruḥam).

A further rule applies to sha’atnez cushions and pillows. The Mishna permits sitting on them “provided one’s flesh does not touch them” (Mishna, Kilayim 9:2). The Yerushalmi explains that this applies only when they are empty and spread flat over a hard surface. If they are stuffed or placed on a soft surface, so that they bend upward around the person sitting on them, one may not sit on them even with an intervening layer (Yerushalmi, Kilayim 9:2; SA YD 301:1). Many explain that this is another application of the prohibition against lying on soft sha’atnez even beneath ten layers of bedding: when the cushions can bend upward, a loose thread may once again wind around the body. Others maintain that the cushions’ bending around the body is itself rabbinically prohibited because it is considered placing sha’atnez upon oneself. Ginat Veradim maintains that this is prohibited by Torah law, as does R. Shlomo Kluger (Tuv Ta’am Va-da’at, 3rd series 2:121). It seems to me that this prohibition applies only when the person sinks into the cushion deeply enough that the sha’atnez fabric at the sides becomes more vertical than horizontal, at which point it can be considered a form of wearing.

Soft sha’atnez upholstery that is stretched tightly over a chair, so that it cannot bend upward around the person sitting on it, is treated like a stiff surface. According to most authorities, one may sit on it as long as clothing or another layer separates it from the skin (Panim Me’irot 2:113; PT YD 301:1; AHS YD 301:9).

The Gemara indicates that a sha’atnez curtain is prohibited because a servant might occasionally wrap himself in it for warmth (Beitza 14b; Rashi). A stiff curtain is permitted, however, since there is no concern that anyone will wrap himself in it (Rambam; Tur; SA YD 301:11). Taz infers from this that one may not lean against the sha’atnez-covered side of a wagon, and Ḥokhmat Adam rules likewise (Taz YD 301:2; Ḥokhmat Adam 106:21). Panim Me’irot, however, permits leaning against sha’atnez fabric that is fixed in place so that it cannot be wrapped around the body. This is also the ruling of PT, Birkei Yosef, Kaf ha-Ḥayim, and Malbushei Yesha (Panim Me’irot 2:113; PT YD 301:1; Birkei Yosef YD 301:6–7; Kaf ha-Ḥayim OḤ 638:52; Malbushei Yesha 5:16).

Even stiff sha’atnez fabric may not be placed upon the body for protection, since protection is one of the functions of clothing. Thus, one may not place a donkey’s sha’atnez saddlecloth on one’s back in order to carry manure on it (SA YD 301:8).

04. What Is Sha’atnez?

To make a garment of wool or linen, the raw materials must undergo three stages alluded to in the word sha’atnez, as the Mishna explains: “Sha’atnez: something that is shua, tavui, and nuz” (Mishna, Kilayim 9:8). First, shua: smoothing the wool or flax by combing. Second, tavui: spinning the fibers into thread. Third, nuz: intertwining, whether by weaving wool and linen threads together as warp and weft to form cloth, or by joining linen thread to a wool garment through tying or sewing.

In practice, wool and linen form prohibited sha’atnez in four principal ways: when raw wool and flax fibers are blended, combed, spun together into thread, and woven into cloth; when wool and linen threads are produced separately and then woven into a single fabric, such as linen warp and wool weft; when wool fabric is sewn or tied with linen thread, or linen fabric with wool thread; and when wool and linen fabrics are sewn together.

What these cases have in common is that the wool and linen underwent all three stages of shua, tavui, and nuz. If they did not undergo all three stages, however, as with felt made by compressing raw wool or flax without spinning or weaving, the overwhelming majority of Rishonim maintain that joining them is not prohibited by Torah law. Rambam disagrees and maintains that even wool and flax that underwent only the first stage of smoothing and combing before being made into felt are prohibited by Torah law when joined.[3]

[3]. There are four approaches to defining the Torah prohibition of sha’atnez.

  1. a) According to Rashi, the Torah prohibition applies only when the wool and flax undergo all three stages together: shua, tavui, and nuz – smoothing, spinning, and weaving. This is also the view of Rivan, Ra’avan, Shibolei ha-Leket, and others. This view appears difficult in light of the Gemara’s statement that tying woolen tzitzit to a linen garment constitutes sha’atnez by Torah law (Yevamot 4a), even though the wool and linen were not processed together. R. Eliyahu Mizraḥi explains that all three stages must be performed together only when wool and flax are woven into a single fabric and can no longer be distinguished from one another. When each material remains distinct – as in a wool fabric joined to a linen fabric, or woolen tzitzit tied to a linen garment – sewing or tying them together violates Torah law. Meiri offers another explanation: because a knot creates a particularly strong bond, it joins the wool and flax even though they did not undergo the three stages together.
  2. b) According to Rabbeinu Tam, Ramban, Rosh, Rashba, Ritva, Semag, Semak, Yere’im, Ran, Peraḥ Shoshan, and others, even if the wool and linen threads were produced separately, weaving them together or joining them by sewing or tying is prohibited by Torah law. This applies only if each thread is plied, meaning that it consists of at least two strands twisted together, since they understand nuz to mean plying. If the threads are unplied, the prohibition is rabbinic. Whether the modern process of roving (mezira) qualifies as plying requires further study.
  3. c) R. Shimshon of Sens accepts all the cases prohibited by Rashi and Rabbeinu Tam but extends the Torah prohibition further: even unplied wool and linen threads are prohibited by Torah law when woven together, sewn together, or tied to one another. In his view, nuz includes any winding together of the materials – thread around thread or thread around fabric. R. Yeruḥam cites this view in the name of Ramah, and it is also the position of Or Zaru’a and Tashbetz. Many Aḥaronim take this view into account (Sefer ha-Zikhronot 3; Ginat Veradim, YD 6:13; Tzemaḥ Tzedek, YD §353). This is the approach presented above.
  4. d) According to Rambam, combining wool and flax that have undergone only smoothing, without spinning or weaving, is prohibited by Torah law. This is also the view of R. Ḥananel, following Rav Ashi (Nidda 61b). Most Rishonim, however, maintain that combining wool and linen felt is prohibited only rabbinically, since the fibers have not undergone all three stages of smoothing, spinning, and intertwining, following Mar Zutra in the same passage. This is the view of Rav Hai Gaon, Rav Sherira Gaon, and all the Rishonim cited in the preceding approaches. There are also several other explanations of Rambam’s position.

05. Threads Composed of Two Species

When a thread is made from sheep’s wool together with another material, such as cotton, its status follows the majority. If it is mostly cotton, the small amount of wool is disregarded, and the thread is considered cotton and may be joined to linen. Likewise, a thread made from hemp and flax may be joined to wool if it is mostly hemp. This principle applies even when raw wool and raw flax have already been mixed together: another material, such as cotton, may be added until it exceeds either the wool or the flax, thereby nullifying that component, and threads made from the resulting mixture are permitted. If the third material does not exceed either the wool or the flax, however, a garment woven from the resulting threads is prohibited by Torah law (Yerushalmi, Kilayim 9:1; SA YD 299:1).

Raw wool and flax can be nullified in a majority, but once they have been spun into thread, they acquire significance and are not nullified even in a thousand times their volume. Thus, a cotton garment sewn with a plied wool-and-linen thread is prohibited by Torah law even if the cotton is a thousand times greater. Likewise, a single wool thread mixed into a large linen garment – or a linen thread into a wool garment – renders the entire garment prohibited. Even if the thread can no longer be located, the garment remains prohibited until it is removed (SA and Rema YD 299:1).[4]

[4]. Raw wool or flax is nullified in a majority because it has not yet acquired independent significance; it still requires processing that will alter its form. Once wool or flax has been spun into thread, however, it acquires significance and is not nullified even when mixed with other threads, such as cotton. Nullification applies only where there is a halakhic conflict between a prohibited substance and a permitted one, and no such conflict exists between a wool or linen thread and other fibers with which it may permissibly be combined. A wool or linen thread is certainly not nullified when combined with the other component of sha’atnez, such as a wool thread in linen fabric or a linen thread in wool fabric, since that combination constitutes the prohibition itself (Tosafot, Nidda 61b, s.v. beged). Thus, even if one end of a long piece of wool fabric is sewn with a single linen thread, the entire fabric may not be worn. This remains true even if most of the fabric lies on the floor and only the other end is wrapped around the body, since the presence of sha’atnez at one end renders the entire garment prohibited for wearing (see SA YD 301:3).

Recycled thread made from shredded worn-out garments is permitted. Although the worn-out garments may include both wool and linen fabrics, once they have been shredded and returned to the state of raw material, any wool or linen present is nullified in the majority. If most of the raw material were wool, the resulting thread would be considered wool, but in practice the likelihood of this is negligible (see Ha-sha’atnez Le-halakha 2, notes 28 and 46; 2:29).

Cushions and linings filled with scraps of worn-out garments are also permitted, even though the scraps were not shredded and may contain intact threads. This is based on a sfek sfeka, a double uncertainty: it is uncertain whether the filling contains both wool and linen – in practice, the likelihood is very low – and even if both are present, it is uncertain whether the sewing thread joins them. If it does not, most authorities maintain that no prohibition applies, even though the wool and linen are enclosed together in a single casing sewn shut on all sides, as explained in SA YD 300:5. Rema records that the accepted custom follows the lenient authorities, as discussed in note 5 (Tiferet Yisrael, Batei Kilayim §118; Ḥeshev ha-Efod 1:64).

Because of marit ayin – concern for appearances – the Sages prohibited threads known as shirayim and kalakh, which resembled wool and linen (Mishna, Kilayim 9:2). Today, however, only actual wool and linen are prohibited, since there is no concern that these other fibers will be mistaken for them. Those familiar with textiles can distinguish them, while those unfamiliar with textiles would not identify them as wool or linen in the first place (see SA YD 298:1; AHS YD 298:5–6).

06. Joining Wool and Linen; Wearing Them Together

Whenever wool and linen are joined directly and securely, the garment is prohibited by Torah law as sha’atnez. Thus, a skirt in which wool and linen fabrics are sewn together, or a wool coat with a linen hanging loop or linen loops, is prohibited by Torah law.

If the wool and linen are not joined to one another, however, most authorities permit the garment. Thus, if wool fabric is sewn to one side of a cotton garment and linen fabric to the other, there is no prohibition, since the wool and linen are not connected. The same applies when pieces of wool and linen are placed inside a lining without being joined to one another (R. Shimshon of Sens; Ramban; Rosh; Rashba). Rambam, by contrast, maintains that once both materials are attached to a single garment, the entire garment is prohibited by Torah law. In practice, the accepted custom follows the lenient view, although the scrupulous are stringent (Rema YD 300:5).[5]

Sha’atnez is prohibited only when wool and linen are joined. When they remain separate, they may be worn together. One may therefore wear a wool shirt over a linen shirt and fasten a belt around both, wear a wool belt with linen pants, or fasten a wool garment to a linen garment with buttons that open easily or with Velcro. In each case, the garments are held together only temporarily and are not permanently joined (SA and Rema YD 300:3–4).[6]

Some maintain that one should not wear wool socks over linen socks, since the linen socks cannot be removed without first removing the wool socks and the two are therefore considered firmly joined (Rema YD 300:4). Most authorities permit this, however, because there is no permanent attachment. This is the accepted practice (SA YD 300:4; Levush; Shakh YD 300:8; AHS YD 300:24).

[5]. The Rishonim disagree whether wool and linen may be joined through an intervening material. The case they discuss concerns a wool garment reinforced and thickened with a leather covering. The leather was sewn to the garment with hemp thread, while the hem along its edge was sewn with linen thread. Rambam rules that “once the wool and linen have been joined in any manner whatsoever, it is kilayim by Torah law” (MT, Laws of Kilayim 10:2). Ra’avad and Orḥot Ḥayim agree, and several Aḥaronim take their stringent view into account (Mishkenot Ya’akov §70; Devar Shmuel §169; Minḥat Yitzḥak 8:117). Others maintain that joining them through an intervening material is prohibited only rabbinically because of marit ayin (Rav Hai Gaon; Ha-Eshkol).

Most Rishonim, however, permit this arrangement as long as the wool and linen are not attached directly to one another, even if the linen thread along the edge of the leather touches the wool. This is the view of R. Shimshon of Sens, Rivmatz, Ramban, Semag, Rashba, Rosh, and others. Rema records that the accepted custom follows the lenient view (Rema YD 300:5). This is also the ruling of Magen Avraham OḤ 9:8, Eliya Rabba OḤ 9:6, MB 9:19, and AHS YD 300:14.

[6]. Sewing wool fabric to linen fabric with hemp thread is prohibited by Torah law whenever the stitching creates a secure attachment. Thus, passing a needle through both fabrics three times is prohibited even without a knot, as is passing it through twice and tying a knot (Rosh; Rema YD 300:2). The same applies when the needle is passed once through the edges of the fabrics and the two ends of the thread are tied together with a double knot (Magen Avraham OḤ 11:13; Ḥavot Ya’ir §143, cited in PT YD 300:2). Some authorities are stringent even when the needle is passed through twice without a knot (MT, Laws of Kilayim 10:24; SA YD 300:2). The Aḥaronim disagree whether fastening wool and linen fabrics together with a safety pin constitutes prohibited sewing or is comparable to fastening them with a button and is therefore permitted (see Malbushei Yesha 3, note 38; Torat ha-Sha’atnez 300:32).

07. Wool and Linen Garments, Past and Present

In the past, most garments were made of wool or linen. Wool is an excellent insulator and keeps the body warm in winter. It also absorbs relatively little dirt, and rain tends to run off it; these qualities made it the standard material for coats. Wool takes dye readily and retains its color, and because it tends to return to its original shape, wrinkles often smooth out on their own. For these reasons, wool garments remain looking new for a relatively long time.

Linen was considered a comfortable, high-quality fabric. Flax fibers are strong, and when spun into fine threads, they can be woven into especially attractive white garments. The natural variations in the thread’s thickness also give linen a distinctive appearance. Linen was so prized that the Sages taught that men in Eretz Yisrael should bring joy to their wives on the festival by giving them pressed linen garments, which women especially appreciated (Pesaḥim 109a). Linen is light and does not insulate, making it well suited to summer clothing through which air can circulate and cool the wearer. Its disadvantages are that it wrinkles easily, absorbs dirt, and is relatively difficult to clean. Once a suitable substitute became available, linen’s status declined sharply.

Cotton, whose production became widespread several centuries ago, is linen’s natural substitute. Although cotton is slightly warmer, it offers several advantages: it is easier to grow and spin, and cotton garments wrinkle less and are easier to wash. Today, the world produces approximately 80 times as much cotton as flax, while most flax is used to make strong thread and for other non-clothing purposes. Because cotton can also be woven into thick winter garments, it has largely replaced wool as well; global cotton production is now approximately 25 times that of wool. Other plant- and animal-based fibers have further reduced wool and linen’s share of the clothing industry.

About three generations ago, manufacturers learned to produce synthetic materials from petroleum byproducts, including plastic, nylon, and synthetic fibers such as polyester and acrylic, from which fabrics can be made. Early synthetic garments were neither breathable nor insulating, causing wearers to suffer from both perspiration and cold; only their low cost allowed them to compete with natural fabrics. As the technology improved, synthetic fabrics became more breathable and insulating. Because they are also less expensive and easier to clean and iron, they became extremely common. By 2018, manufactured fibers accounted for more than 70 percent of global fiber production, up from 60 percent a decade earlier. Wool and linen together accounted for only about 1 percent of the clothing industry, and their share appeared likely to continue declining[7]

In practice, little linen clothing remains apart from a small number of luxury shirts and suits. Because linen thread and fabric are strong, however, they are sometimes used to reinforce parts of coats and suits, such as collars and the areas where buttons and buttonholes are sewn.

Wool garments have also become less common for the reasons discussed above. Nevertheless, wool’s warmth and resistance to rain and dirt make wool sweaters attractive to those who prefer a natural, breathable material, while its prestigious appearance and durability lead many to choose wool suits and coats.

[7]. According to data from DNPI, global fiber production reached approximately 111 million metric tons in 2018. Of this total, only 29 percent – about 32 million tons – consisted of natural fibers derived from plants or animals, such as cotton, jute, wool, linen, ramie, and silk; the remaining 71 percent consisted of manufactured fibers. Cotton accounted for 23.5 percent of global production, or 26.1 million tons; wool accounted for 1 percent, or 1.08 million tons; and linen for approximately 0.3 percent, or 310,000 tons. Wool and linen together thus represented only slightly more than 1 percent of all fibers produced, approximately 1.3 percent. The overall trend is toward a declining share of natural fibers relative to manufactured ones.

08. Avoiding Sha’atnez in Practice

The overwhelming majority of garments sold today raise no concern of sha’atnez, since they are made from synthetic materials or cotton. Thus, if a garment’s label states that its main material is synthetic, cotton, or any other fiber that is neither wool nor linen, there is no need for concern. In rare cases, such a garment may have a wool or linen ornament or be sewn with linen thread; in even rarer cases, it may contain both linen thread and a wool ornament. This possibility is so remote that it may be disregarded. Moreover, according to most authorities, no prohibition applies unless the wool and linen are joined to one another (above, 6). One should therefore read the label, and if it does not list wool or linen, there is no concern of sha’atnez.

For wool and linen garments as well, it is sufficient for the buyer to examine the label. If it states that the garment is made of wool or linen together with other materials, but does not list both wool and linen, the garment does not require testing. Labels are sometimes inaccurate, either because manufacturers are not required to list wool or linen content of only one or two percent, or because, on rare occasions, the wrong label is attached to a garment. In practice, however, as long as the label does not state that the garment contains both wool and linen, the likelihood that it contains sha’atnez is far below a mi’ut ha-matzui – a frequency common enough to require concern – and it need not be tested. The same is true of ordinary wool suits and coats, since the possibility that linen has been added is too remote to warrant concern.

Very expensive wool suits and coats, however, require greater caution. Some are hand-sewn with linen thread, reinforced around the collar or buttons with sturdy linen fabric, or fitted with linen interfacing in the shoulders and chest. Since linen is found in a mi’ut ha-matzui of such garments, any very expensive wool suit or coat must be tested. It is likewise proper to test a linen suit, since wool may have been used in its collar.

At a sha’atnez laboratory, garments are examined under a microscope, enabling trained specialists to identify wool, linen, and other fibers by their distinctive structures. As a rule, these laboratories take into account even the stringent views of individual authorities, both in defining sha’atnez and in determining when testing is required.

The rules discussed above apply to individual buyers. Clothing retailers, however, must take greater care to avoid exposing the public to sha’atnez. Whenever their experience with the merchandise gives them some reason to suspect that a shipment of wool or linen garments may contain sha’atnez, they should send a representative sample for testing, even if the likelihood is below a mi’ut ha-matzui. If the sample contains no sha’atnez, the remaining garments in that line need not be tested. When their experience provides no basis for concern, no testing is necessary; when the concern is substantial, as with expensive suits and coats, the entire shipment should be tested.

Buyers should preferably purchase wool or linen garments from God-fearing retailers who take care not to expose their customers to sha’atnez. Nevertheless, when such garments are purchased from an ordinary store, only especially expensive wool suits and coats and linen suits require testing.[8]

[8]. The Mishna lists types of garments purchased from non-Jews that require inspection because they were sometimes made with sha’atnez, as well as garments that do not require inspection because the wool was sewn with hemp rather than linen thread (Mishna, Kilayim 9:7). The Yerushalmi adds that once linen became readily available everywhere, all wool garments required inspection (Yerushalmi, Kilayim 9:7). Accordingly, SA rules that one who purchases a wool garment from a non-Jew must inspect it to determine whether it was sewn with linen thread. In places where linen is more expensive than hemp, however, no inspection is necessary, since it may be assumed that hemp thread was used (SA YD 302:2).

In recent generations, the garment industry has become vastly more sophisticated and diverse, and the clothing trade now spans countries and continents. It is therefore no longer possible to establish fixed rules for every type of garment. Contemporary authorities rule that each category must instead be assessed according to the halakhic principles of majority and minority (see Igrot Moshe, YD 1, end of §72; Ha-sha’atnez Le-halakha 7:2–3). When the likelihood of sha’atnez reaches the level of a mi’ut ha-matzui – a frequency common enough to require concern – testing is required rabbinically. Only in pressing circumstances, when testing is entirely impossible, may one be lenient. If the likelihood is lower, no testing is required.

As explained in Peninei Halakha: Kashrut 23:5, note 6, some maintain that a mi’ut ha-matzui is a frequency of approximately 25–49 percent, while any lower frequency is considered an uncommon minority (Rivash). Others maintain that only a frequency below ten percent is considered uncommon (Mishkenot Ya’akov), and this is the standard ruling in practice. It appears that these percentages should be calculated separately for each category of garment: wool coats apart from coats made from other fabrics; ordinary wool suits apart from luxury wool suits and suits made from other materials; wool sweaters apart from other sweaters; and so forth.

It appears, however, that clothing retailers have a greater responsibility to investigate, for three reasons. First, an error on their part could cause many customers to violate the prohibition, and matters affecting the public require greater caution. The same principle applies to a public mikveh, where all halakhic opinions are taken into account because it serves the public (see Yabi’a Omer 6, YD §15). Second, retailers are better positioned to investigate. Their familiarity with the merchandise enables them to recognize when there is cause for concern, they can readily ask the manufacturer which materials were used, and they can have a representative sample tested. Since the leniency not to test when the likelihood is below a mi’ut ha-matzui is based on the burden involved, retailers, for whom testing is less burdensome, bear a greater responsibility to investigate (see Peninei Halakha: Kashrut 20:4; 38:9, note 8). Third, whether testing is considered unduly burdensome depends on the scale of what is being examined. A shoḥet need not spend several hours examining a single animal. If a few hours of work would benefit many animals, however, he would be required to investigate even remote concerns. The same applies to sha’atnez.

09. Discovering Kilayim in One’s Garment

In the past, sha’atnez was often readily identifiable, since most threads and fabrics were made of wool or linen and many people knew how to distinguish them. Some garments were so obviously sha’atnez that, within the Jewish community, any Jew who wore them was understood to be openly defying Jewish practice and desecrating God’s name. Other garments were known by most Jews to contain sha’atnez, although not everyone could recognize it, while still others could be identified only by experts. A person might therefore buy and put on a garment, only to discover while standing in the marketplace that he was wearing sha’atnez prohibited by Torah law. He must then remove it immediately, even if this leaves him naked and humiliated in the street, for “there is no understanding and no counsel against the Lord”: wherever God’s name is desecrated, honor is not accorded even to a rabbi (Berakhot 19b; SA YD 303:1).

If he refuses to remove the garment because he is embarrassed, some authorities maintain that the mitzva of rebuke and the mutual responsibility shared by all Jews require another Jew to tear the garment off him (Rambam; SA YD 303:1). This applies only when the wearer accepts the halakha but finds it difficult to comply; in such a case, it may be assumed that he will ultimately be grateful to the person who tore off the garment and prevented him from violating the prohibition. If, however, he has cast off the yoke of the mitzvot, tearing off the garment will not bring him closer to Torah and mitzvot and should not be done. Many authorities maintain that even when the wearer accepts the halakha in principle, one should rebuke him but may not tear the garment from him (Rosh; Rashba; Ra’ah; Terumat Ha-deshen).

The authorities disagree about what one should do upon seeing someone unknowingly wearing a sha’atnez garment when removing it immediately would cause him severe embarrassment. Many maintain that one should not inform him on the spot, since doing so would force him to undress publicly. Instead, one should invite him home and tell him there that the garment contains sha’atnez (Rosh; Terumat Ha-deshen; Rema). Others maintain that he must be informed immediately so that he can remove the garment without delay (Rambam; Radbaz).[9]

[9]. The Gemara states: “One who discovers kilayim in his garment must remove it even in the marketplace. ‘There is no wisdom, no understanding, and no counsel against the Lord’ – wherever desecration of God’s name is involved, no honor is accorded even to a teacher” (Berakhot 19b). The Gemara concludes that human dignity overrides a rabbinic prohibition but does not override a Torah prohibition when the violation requires an action. Although a person who continues wearing sha’atnez is not performing a new act, the violation began when he put on the garment, and his continued wearing is therefore also considered an active violation. The Yerushalmi records two opinions. According to one, the wearer must remove the sha’atnez garment. According to the other, “so great is human dignity that it temporarily overrides a negative commandment” (Yerushalmi, Kilayim 9:1). Some explain that a garment containing sha’atnez by Torah law must be removed, whereas one containing only rabbinically prohibited sha’atnez need not be removed, in accordance with the Bavli (Mahara Fulda; Sefer Ḥaredim). Others understand the second opinion in the Yerushalmi to mean that, for a limited time, human dignity overrides even a Torah prohibition involving an active violation (Rash Sirilio; Maharam b. Ḥaviv). A third interpretation maintains that the dispute concerns whether one must inform someone who is unknowingly wearing kilayim, or whether one should spare him the embarrassment of having to remove the garment in public (based on Rosh).

According to Rambam, one who sees another person – even his teacher – wearing kilayim prohibited by Torah law must “rush over and tear the garment off him immediately” (MT, Laws of Kilayim 10:29). This ruling is based on Rambam’s version of the Gemara. Radbaz and Kesef Mishneh explain that Rambam understood the incident involving Rav Adda b. Ahava accordingly: he tore a woman’s garment because he mistakenly believed that she was Jewish and was wearing kilayim prohibited by Torah law (Berakhot 20a). This is also the ruling of SA YD 303:1 and Sha’agat Aryeh §58.

Rosh, however, understands Berakhot 19b differently. If one sees another person deliberately wearing kilayim, he must rebuke him, even though compliance will require the wearer to remove the garment in public and suffer embarrassment. Rosh makes no mention of tearing the garment. If the person put on the sha’atnez unknowingly, however, one should not inform him until he reaches home, so that he will not be humiliated by having to remove it in public. Rosh derives this distinction from the Yerushalmi. This is also the view of Terumat Ha-deshen, Rema, Rash Sirilio, Baḥ – who maintains that Rambam agrees – and Peri Yitzḥak 1:26.

Other Rishonim explain that the Gemara discusses a person who suddenly discovers kilayim in his own garment and is therefore required to remove it. It does not address whether someone else must inform an unaware wearer when doing so will cause him public embarrassment (Rashba; Ra’ah; Orḥot Ḥayim; Meiri). It appears that these authorities agree in practice with Rosh, since they too recognize the obligation to rebuke another person in accordance with the laws governing rebuke. In any event, none of the authorities who disagree with Rambam suggest tearing another person’s garment in order to save him from the prohibition; their discussion concerns rebuke alone.

10. Kilayim in the Priestly Garments and Tzitzit

Although the Torah prohibits sha’atnez, it requires wool and linen to be combined in two mitzvot involving clothing: the priestly garments and tzitzit.

During the Temple service, every kohen wore four garments: a tunic, breeches, and a turban, all made of white linen, and a sash woven from both wool and linen. The sash was made from four threads: one of white linen and three of dyed wool – tekhelet (sky blue), argaman (purple), and tola’at shani (crimson). The dyed threads were made of wool because wool absorbs dye well. The Kohen Gadol wore four additional garments: the robe, the efod (apron-like garment), the ḥoshen (breastplate), and the tzitz (frontlet). The Torah requires wool and linen to be combined in the efod and the ḥoshen. Kohanim were permitted to wear these sha’atnez garments only while serving in the Temple. Upon leaving the Temple, they had to remove the priestly garments to avoid violating the prohibition of sha’atnez.[10]

Regarding tzitzit, the Torah states: “You shall not wear sha’atnez, wool and linen together. You shall make tassels for yourself on the four corners of the garment with which you cover yourself” (Devarim 22:11–12). From the juxtaposition of these verses, the Sages derived that sha’atnez is permitted for the mitzva of tzitzit. The mitzva requires the tassels placed on the corners of the garment to contain both white and tekhelet threads. Since tekhelet threads were made of wool, attaching them to a linen garment creates sha’atnez; nevertheless, the Torah commands it. This teaches a general principle: whenever a positive mitzva conflicts with a prohibition, the positive mitzva takes precedence and the prohibition is set aside (Yevamot 4a–b).

The Sages nevertheless decreed that woolen tekhelet threads not be attached to a linen garment and that only white tzitzit threads be used. They were concerned that one might wear the garment at night, when one is exempt from tzitzit, and thereby violate the prohibition of sha’atnez (Menaḥot 40a–b; Shabbat 25b; MT, Laws of Tzitzit 3:6–7).[11]

[10]. The Kohen Gadol wore a sha’atnez sash each day, as the Torah states: “The sash was of twined linen, tekhelet, argaman, and tola’at shani, the work of an embroiderer, as the Lord commanded Moshe” (Shemot 39:29). Before entering the Holy of Holies on Yom Kippur, however, he wore only linen garments, including a linen sash, as the Torah states: “He shall gird himself with a linen sash” (Vayikra 16:4). Yeḥezkel likewise states: “When they enter the gates of the inner courtyard, they shall wear linen garments; no wool shall come upon them” (Yeḥezkel 44:17).

The Gemara disagrees as to whether the sash of an ordinary kohen was sha’atnez like that of the Kohen Gadol (Yoma 6a, 12a, 69a). The halakha follows the view that it was (MT, Laws of the Temple Vessels 8:1–2). According to Rambam, the kohanim were permitted to wear the sash only while performing the Temple service (ibid. 8:11; MT, Laws of Kilayim 10:32). Other authorities permit them to wear it for as long as they remained in the Temple (Ra’avad on MT, Laws of the Temple Vessels 8:11; Tosafot, Menaḥot 41a; Rosh; Sha’agat Aryeh, old edition, §§29–30).

[11]. As explained above, the Sages derived from the juxtaposition of the verses that the mitzva of tzitzit overrides the prohibition of sha’atnez, permitting linen threads to be placed on a wool garment and wool threads on a linen garment (Yevamot 4a–b). Rav Yehuda rules likewise (Menaḥot 39b). The Gemara concludes, however, in accordance with Reish Lakish: “Whenever you find a positive commandment and a prohibition, if you can fulfill both, that is preferable; if not, let the positive commandment override the prohibition” (Menaḥot 40a). On this basis, Rambam rules that on a wool garment, the white threads must also be wool and may not be linen.

Others maintain that there is no contradiction between Rav Yehuda and Reish Lakish (Tosafot, Yevamot 4b, s.v. de-afilu; Tur). Sha’atnez in tzitzit follows a special rule: once the mitzva is properly fulfilled with tekhelet, sha’atnez is permitted even when not strictly necessary. Thus, white woolen threads may also be attached to a linen garment. Rashba and Ritva explain Reish Lakish differently: if the owner of a linen garment can obtain white linen threads, he must use them rather than resort unnecessarily to wool. If he cannot obtain them, however, even though they are generally available, he may use white woolen threads, as Shmuel and Rav Yehuda rule. One view in Tosafot maintains that the Amoraim do not disagree at all: by Torah law, sha’atnez is entirely permitted in tzitzit, while rabbinic law permits it only when necessary.

Although by Torah law the mitzva of tzitzit overrides the prohibition of kilayim, the people of Jerusalem did not attach tekhelet to linen garments. Rabbi explained that the Sages enacted this decree “because they are not proficient,” lest people come to use kilayim when no mitzva applies (Menaḥot 40a). According to Rif, Rashi, Rambam, Ramban, Rashba, and R. Yeruḥam, the decree prohibited woolen tekhelet threads but permitted white linen threads. Rav Hai Gaon, Rav Amram Gaon, Rabbeinu Tam, Ittur, Semag, and Semak maintain that the Sages prohibited attaching any tzitzit to a linen garment, lest one attach tekhelet and violate the prohibition. In practice, SA and Rema rule that ideally one should take into account the view of Rabbeinu Tam and those who follow him and avoid making a linen tallit. A person who has no wool tallit, however, should fulfill the mitzva with a linen tallit and linen tzitzit, in accordance with Rif and those who follow him (SA OḤ 9:6).

11. Reasons for the Mitzva

The prohibitions of kilayim and sha’atnez are divine statutes whose essential meaning lies beyond human understanding. Even so, the Sages throughout the generations have proposed various explanations for the mitzva. The central explanation is that wool and linen possess different qualities and each has its own purpose; God therefore commanded us to give each its proper place and not mix them (Ramban, Vayikra 19:19).

Wool and linen were the two principal materials used for clothing, yet they differ fundamentally and even stand in opposition. Wool comes from the animal world and alludes to the attribute of ḥesed, while linen comes from the plant world and alludes to the attribute of din; combining them is therefore complex and difficult. The Torah commanded that they be joined only in the context of a mitzva – in the priestly garments and in tzitzit – so that their union takes place in holiness and each power finds its proper expression, adding blessing and life. Moreover, since combining wool and linen is a mitzva in the priestly garments and in tzitzit, it is inappropriate to use this unique union for ordinary purposes, as it is reserved for holiness alone (Da’at Zekenim, Devarim 22:11; Ḥizkuni, Vayikra 19:19; Metzudat David of Radbaz §235; Likutei Halakhot, Kilei Begadim 1).

It has also been explained that these opposing forces can find their proper expression only in the context of a mitzva. When they are combined outside that context, their positive potential is constrained and prevented from emerging (Zohar III 86b). Within a mitzva, ḥesed and din are expressed properly; when mixed indiscriminately, however, the evil inclination turns them to harmful ends (Mikhtav Me-Eliyahu IV, p. 176). When a person ought to give tzedaka, for example, the evil inclination may cloak itself in din and argue that the poor person is undeserving. Conversely, when one must stand for truth and rescue someone being exploited by an oppressor, the evil inclination may cloak itself in ḥesed and find merit in the oppressor, thereby evading the obligation to help the victim.

It may be suggested that by separating wool and linen – the two natural fibers best suited for clothing – and permitting their union only in the context of a mitzva, the Torah taught humanity to develop additional fibers in which the human role in combining and shaping natural properties is more pronounced. Combining such fibers is therefore straightforward and carries neither a prohibition nor a mitzva.[12]

[12]. The Sages further taught that the root of the evil associated with combining wool and linen is alluded to in the offerings of Kayin and Hevel, which led to the first murder. The Torah recounts: “In the course of time, Kayin brought an offering to the Lord from the fruit of the ground. Hevel also brought from the firstborn of his flock and from their choicest parts. The Lord regarded Hevel and his offering, but Kayin and his offering He did not regard. Kayin became greatly distressed, and his face fell…. Kayin rose against his brother Hevel and killed him” (Bereishit 4:3–5, 8). The Sages identify Kayin’s offering from the ground with flax, and Hevel’s offering of a sheep, whose wool remained on it, with wool. We were therefore commanded not to combine the offering of the righteous with the offering of the wicked (Tanḥuma, Bereishit 9; Pirkei de-R. Eliezer 21).

It may be suggested further that had Kayin brought his flax offering on its own, it would have been accepted. That offering reflected his own spiritual level: he was a tiller of the soil and brought an offering from what he had grown. Once he saw Hevel bring a far superior offering – a sheep whose wool had not yet been shorn – he faced a difficult test. Would he humble himself and learn from his brother how to serve God with greater excellence, perhaps even asking Hevel to serve as his kohen? Or would he envy his brother for having found greater favor in God’s eyes and murder him? To protect us from such trials, the Torah commanded us not to combine these two materials except in the context of a mitzva (see Zohar III 87a).

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