שֶׁלֹּא לִלְבֹּשׁ שַׁעַטְנֵז – שֶׁלֹּא נִלְבַּשׁ בֶּגֶד הַמְחֻבָּר מִצֶּמֶר וּפִשְׁתִּים, וְזֶהוּ נִקְרָא שַׁעַטְנֵז, וְעַל זֶה נֶאֱמַר (דברים כב יא) לֹא תִלְבַּשׁ שַׁעַטְנֵז צֶמֶר וּפִשְׁתִּים יַחְדָּו. To not wear shaatnez: To not wear clothing that is composed of wool and flax (linen), and that is what is called, shaatnez. And about this is it stated (Deuteronomy 22:11), “You shall not wear shaatnez, wool and flax together.”
רֶמֶז מִשָּׁרְשֵׁי הַמִּצְוָה. כָּתַבְתִּי בְּסֵדֶר מִשְׁפָּטִים בְּעִנְיַן מְכַשֵּׁפָה לֹא תְחַיֶּה (מצוה סב). וְהָרַמְבַּ"ם זִכְרוֹנוֹ לִבְרָכָה כָּתַב (בסהמ"צ ל"ת מב ובמורה נבוכים ח"ג פל"ז) בְּטַעַם הָאִסּוּר, לְפִי שֶׁהָיוּ כּוּמָרֵי עֲבוֹדָה זָרָה לוֹבְשִׁין בַּזְּמַן הַהוּא כֵּן, וְהוּא כָּתַב עוֹד כִּי הַיּוֹם עֲדַיִן מְפֻרְסָם הַדָּבָר אֵצֶל כּוּמָרִים שֶׁיֵּשׁ בְּמִצְרַיִם. I wrote a hint about the roots of the commandment in the Order of Mishpatim about the matter of “do not keep a witch alive” (Sefer HaChinukh 62). And Rambam, may his memory be blessed, wrote about the explanation of the prohibition (in Sefer HaMitzvot, Negative Commandments 42 and in Guide for the Perplexed 3:37), [that] it is because the priests of idolatry would dress like this at that time. And he wrote further that this matter is still known with the priests that are in Egypt.
מִדִּינֵי הַמִּצְוָה. מָה שֶׁאָמְרוּ זִכְרוֹנָם לִבְרָכָה (יבמות ה, ב רמב"ם כלאים י, ב) שֶׁאֵין אָסוּר מִן הַתּוֹרָה מַחְבֶּרֶת צֶמֶר וּפִשְׁתִּים אֶלָּא בְּשׁוּעַ טָווּי וְנוּז, כְּלוֹמַר שֶׁהַצֶּמֶר שׁוּעַ בִּפְנֵי עַצְמוֹ, כְּלוֹמַר טָרוּף וְטָווּי בִּפְנֵי עַצְמוֹ, וְנוּז בִּפְנֵי עַצְמוֹ, פֵּרוּשׁ נוּז שָׁזוּר (עי' נדה סא ב ברש"י ור"ת שם בתוס'), וְכֵן הַפִּשְׁתָּן כְּמוֹ כֵן שׁוּעַ טָווּי וְנוּז בִּפְנֵי עַצְמוֹ, וְאַחַר כָּךְ חִבְּרָם יַחַד כְּגוֹן שֶׁאֲרָגָן אוֹ אֲפִלּוּ קְשָׁרָן זֶה בָּזֶה, מִכֵּיוָן שֶׁעָשָׂה בָּהֶן שְׁנֵי קְשָׁרִים זֶהוּ שַׁעַטְנֵז דְּאוֹרָיְתָא לִלְקוֹת עָלָיו, אֲבָל כָּל זְמַן שֶׁלֹּא נַעֲשׂוּ בָּהֶן שְׁלֹשׁ הַמְּלָאכוֹת שֶׁכָּתַבְנוּ אֵין זֶה שַׁעַטְנֵז דְּאוֹרָיְתָא אֶלָּא מִדְּרַבָּנָן, כְּדַעַת קְצָת הַמְּפָרְשִׁים, וְאֵין לוֹקִין עָלָיו, אֲבָל מִדְּרַבָּנָן אָסוּר כָּל שֶׁנַּעֲשָׂה בָּהֶן אַחַת מִן הַמְּלָאכוֹת שֶׁזָּכַרְנוּ אוֹ שׁוּעַ אוֹ טָווּי אוֹ נוּז, וְזֶהוּ אָמְרָם זִכְרוֹנָם לִבְרָכָה (כלאים פ"ט מ"ט) הַלְּבָדִין אֲסוּרִין, כְּלוֹמַר מִדְּרַבָּנָן, מִפְּנֵי שֶׁהוּא שׁוּעַ. וּמִן הַמְּפָרְשִׁים שֶׁאָמְרוּ דְּבִמְלָאכָה אַחַת מֵאֵלּוּ אֲסוּרִין מִדְּאוֹרַיְתָא, וּכְשֶׁאָמְרוּ בְּכָאן אֲסוּרִין, כְּלוֹמַר מִדְּאוֹרַיְתָא. From the laws of this commandment is that which they, may their memory be blessed, said (Yevamot 5b, and see Mishneh Torah, Diverse Species 10:2) that there is only a prohibition from Torah writ of a combination of wool and flax if they are shua, tavui and noz. [This] is to say that the wool is shua by itself, meaning to say, beaten, and tavui (spun) by itself and noz by itself — and the explanation of noz is woven (see Rashi on Niddah 61b and Rabbenu Tam in Tosafot on Niddah 61b) — and so [too] is the flax shua, tavui and noz by itself; and afterwards he combined them together — for example, he wove them, or even if he tied them one to another, once he tied two knots, this is shaatnez from Torah writ, for which there is lashing. But the whole time that these three [processes] that we have written are not done to them, it is not shaatnez from Torah writ, but [only] rabbinically, according to the opinion of some commentators, and we do not administer lashes for it. But it is forbidden rabbinically if one of the [processes] that we have mentioned — either shua or tavui or noz — is done to them. And this is what they, may their memory be blessed, said (Mishnah Kilayim 9:9), “the ones alone are forbidden” — meaning to say, rabbinically. And there are some commentators that said that [even] with one of these [processes], it is forbidden from Torah writ — and when they said about this, “forbidden,” it is meaning to say from Torah writ.
וְאָמְרוּ זִכְרוֹנָם לִבְרָכָה (יומא סט, א) בְּעִנְיָן זֶה, אֲפִלּוּ עֲשָׂרָה מַצָּעוֹת זֶה עַל גַּב זֶה וְכִלְאַיִם תַּחְתֵּיהֶן אָסוּר לֵשֵׁב עֲלֵיהֶן, דְּחָיְשִׁינַן שֶׁמָּא תִּכָּרֵךְ נִימָא עַל בְּשָׂרוֹ, וְדָבָר זֶה אָמְרוּ זִכְרוֹנָם לִבְרָכָה (רמב"ם שם ה' יב, יג), כְּשֶׁאוֹתָן הַכִּלְאַיִם אֲשֶׁר מִתַּחַת הֵן רַכִּין, כִּי אָז יֵשׁ בַּדָּבָר חֲשָׁשׁ זֶה שֶׁל כְּרִיכָה, וְאִסּוּר זֶה הוּא מִדְּרַבָּנָן, דְּאִלּוּ מִדְּאוֹרַיְתָא מֻתָּר וַאֲפִלּוּ כְּשֶׁהֵן רַכִּין, וּכְמוֹ שֶׁאָמְרוּ זִכְרוֹנָם לִבְרָכָה (שם) לֹא יַעֲלֶה עָלֶיךָ (ויקרא יט, יט), אֲבָל אַתָּה מַצִּיעוֹ תַּחְתֶּיךָ. וּבַיְּרוּשַׁלְמִי (כלאים ט, א) אָמְרוּ דְּכָרִים וּכְסָתוֹת אַף עַל פִּי שֶׁהֵן קָשִׁים בִּמְלֵאִים אָסוּר לֵשֵׁב עֲלֵיהֶן מִדְּרַבָּנָן, לְפִי שֶׁהֵן נִכְפָּלִים עַל הַיּוֹשֵׁב בָּהֶם אֲבָל (בירושלמי בְּרֵיקָן) בְּרַכִּין דְּלֵיכָּא חֲשַׁשׁ הַעֲלָאָה מֻתָּר לֵשֵׁב בָּהֶן, מִכֵּיוָן שֶׁהֵם קָשִׁין. וְטַעַם הָעִנְיָן מִפְּנֵי שֶׁהַכָּתוּב אָסַר שַׁעַטְנֵז בִּלְשׁוֹן לְבִישָׁה, כְּלוֹמַר דֶּרֶךְ מַלְבּוּשׁ הוּא שֶׁאָסוּר וְלֹא בְּעִנְיָן אַחֵר. וּמִטַּעַם זֶה הִתִּירוּ לָנוּ מוֹרֵינוּ יִשְׁמְרֵם אֵל, לָתֵת עַל רֹאשֵׁנוּ כּוֹבָעִים הָעֲשׂוּיִים מִלְּבָדִים לְהָגֵן מִן הַשֶּׁמֶשׁ, מִפְּנֵי שֶׁהֵם גַּם כֵּן קָשִׁים מְאֹד, וּלְפִיכָךְ אַף עַל פִּי שֶׁיֵּשׁ בָּהֶן כִּלְאַיִם הִתִּירוּ אוֹתָן, לְפִי שֶׁאֵין דֶּרֶךְ לְבִישָׁה בְּדָבָר קָשֶׁה כָּל כָּךְ, וְיֵשׁ שֶׁרוֹצֶה לְהַחְמִיר עַל עַצְמוֹ בָּזֶה, וְלֹא מִחוּ בְּיָדוֹ. וּמִטַּעַם זֶה שֶׁדֶּרֶךְ מַלְבּוּשׁ אָסְרָה תּוֹרָה הִתִּירוּ גַּם כֵּן לְמוֹכְרֵי כְּסוּת לִמְכֹּר כְּדַרְכָּן, וּבִלְבַד שֶׁלֹּא יְכַוְּנוּ לְהִתְחַמֵּם בָּהֶן כְּלָל, וּמִכָּל מָקוֹם אַף עַל פִּי שֶׁהִתִּירוּ דָּבָר זֶה, הַסַּרְסוּרִין הַצְּנוּעִים וְטוֹבִים מַפְשִׁילִים בִּגְדֵי הַכִּלְאַיִם כְּשֶׁמּוֹכְרִין אוֹתָם בְּמַקֵּל לַאֲחוֹרֵיהֶן, שֶׁלֹּא יִגְּעוּ בָּהֶן. וְאָמְרוּ זִכְרוֹנָם לִבְרָכָה (רמב"ם שם ה"ה), שֶׁהַכִּלְאַיִם אֵין לָהֶן שִׁעוּר, אֲפִלּוּ חוּט אֶחָד בְּבֶגֶד גָּדוֹל אוֹסֵר הַכֹּל עַד שֶׁיָּסִיר אוֹתוֹ. הַכָּלָךְ (רמב"ם שם ה"א), שֶׁהוּא כְּעֵין צֶמֶר, וְהוּא גָּדֵל עַל הָאֲבָנִים שֶׁבְּיָם הַמֶּלַח, אָסוּר עִם הַפִּשְׁתָּן מִדְּרַבָּנָן, מִפְּנֵי מַרְאִית הָעַיִן. וְיֶתֶר פְּרָטֵי הַמִּצְוָה, מְבֹאָרִים בְּמַסֶּכֶת כִּלְאַיִם (פ"ט) וּבְמַסֶּכֶת שַׁבָּת וּבְסוֹף מַכּוֹת. And they, may their memory be blessed, said about this matter (Yoma 49a), “Even [if there are] ten beddings, one on top of the other, it is forbidden to [sit] upon them,” as we are concerned lest a fiber wrap itself upon his flesh. And they, may their memory be blessed, said this matter when the forbidden mixture underneath is soft, as then is there this concern of wrapping. (See Mishneh Torah, Diverse Species 5:12-13.) And this prohibition is rabbinic, as from Torah writ it is permissible, even when they are soft. And [it is] as they, may their memory be blessed, said, “‘It shall not come upon you’ (Leviticus 19:19) — but you can set it under you.” (See Mishneh Torah, Diverse Species 10:12-13.) And in Yerushalmi Kilayim 9:1, they said [that] pillows and comforters — even though they are hard — with full ones, it is forbidden to sit upon them rabbinically, since they double over on the one that is sitting upon them; but with empty ones ([this is what is written] in the Yerushalmi, [though there appears to be an error here in the Sefer HaChinukh, wherein it is written], the soft ones), since there is no concern that they will go on top, it is permissible to sit upon them, since (if) they are hard. And the explanation of the matter is [that it is] because the verse forbids shaatnez with an expression of wearing, meaning to say in the way of wearing is it forbidden and not in another way. And for this reason our teacher, God protect him, permitted us to put hats that are made from felt on our head to guard against the sun, since they are also very hard. And therefore, even though they have a forbidden mixture in them, they permitted them — as it is not the way of wearing something so hard. And there is one who wants to be stringent upon himself with this, and they did not protest against him. And for this reason — that it is the way of wearing that the Torah forbade — they also permitted the sellers of cloth to sell according to their way (to put the cloth on top of themselves) but only when they do not have any intention at all to warm up from it. And nonetheless, the modest and good wholesalers extend clothes from forbidden mixtures on a stick behind them so that they not touch them. And they, may their memory be blessed, said that there is no measurement to forbidden mixtures — that even one string in a large garment forbids all of it until he removes it. (See Mishneh Torah, Diverse Species 10:5.) Kelech — which is a type of wool and it grows on stones in the Dead Sea — is forbidden with flax rabbinically, because of the appearance [of sin] (marait ayin). And the rest of the details of the commandment are elucidated in Mishnah Kilayim 9 and in Tractate Shabbat and in the end of Makkot.
וְנוֹהֵג אִסּוּר זֶה בְּכָל מָקוֹם וּבְכָל זְמַן, בִּזְכָרִים וּנְקֵבוֹת. וְהָעוֹבֵר עַל זֶה וְלָבַשׁ כִּלְאַיִם דְּאוֹרָיְתָא אוֹ הִתְכַּסָּה בָּהֶן, חַיָּב מַלְקוּת. וּבְכִלְאַיִם דְּרַבָּנָן חַיָּב מַכַּת מַרְדּוּת. וְהַלּוֹבֵשׁ כִּלְאַיִם וַאֲפִלּוּ כָּל הַיּוֹם כֻּלּוֹ אֵינוֹ לוֹקֶה אֶלָּא אַחַת, אֲבָל הוֹצִיא רֹאשׁוֹ מִן הַבֶּגֶד וְהֶחְזִירוֹ, הוֹצִיא רֹאשׁוֹ וְהֶחְזִירוֹ, אַף עַל פִּי שֶׁלֹּא פָּשַׁט הַבֶּגֶד כֻּלּוֹ, חַיָּב עַל כָּל אַחַת וְאַחַת. וּבַמֶּה דְּבָרִים אֲמוּרִים שֶׁהוּא חַיָּב אַחַת עַל כָּל הַיּוֹם כֻּלּוֹ? כְּשֶׁהִתְרוּ בּוֹ הַתְרָאָה אַחַת, אֲבָל אִם הִתְרוּ בּוֹ וְאָמְרוּ לוֹ פְּשֹׁט וְהוּא לָבוּשׁ בּוֹ, וְשָׁהָה כְּדֵי לִלְבֹּשׁ וְלִפְשׁוֹט אַחַר שֶׁהִתְרוּ בּוֹ, הֲרֵי זֶה חַיָּב עַל כָּל שְׁהִיָּה וּשְׁהִיָּה שֶׁהִתְרוּ בּוֹ עָלֶיהָ, וְאַף עַל פִּי שֶׁלֹּא פָּשַׁט. And this prohibition is practiced in every place and at all times by males and females. And one who transgresses it, and wears a Torah-level forbidden mixture — or covers himself with it — is liable for lashes. And if it is a rabbinic-level forbidden mixture, he is liable for lashes of rebellion. And one who wears a forbidden mixture — and even if he wears it the entire day — is only lashed one [set of lashes]. But one who takes his head out from the garment and puts it back in — even though he does not remove the entire garment — is obligated [lashes] for each and every [time that he does this]. And in what case does it apply that he is only obligated once for [wearing it] the whole day? When they gave him one warning. But if they warned him [several times] and they said to him, “Take it off,” and he [continues to] wear it for the time period [needed] in order to put it on and take it off — since they warned him, behold, he is obligated for each and every [such] time period that they warned him about it, and even though he did not take [it] off [and put it on anew].