(ט) לֹא־תִזְרַ֥ע כַּרְמְךָ֖ כִּלְאָ֑יִם פֶּן־תִּקְדַּ֗שׁ הַֽמְלֵאָ֤ה הַזֶּ֙רַע֙ אֲשֶׁ֣ר תִּזְרָ֔ע וּתְבוּאַ֖ת הַכָּֽרֶם׃
(י) לֹֽא־תַחֲרֹ֥שׁ בְּשׁוֹר־וּבַחֲמֹ֖ר יַחְדָּֽו׃ (ס)
(יא) לֹ֤א תִלְבַּשׁ֙ שַֽׁעַטְנֵ֔ז צֶ֥מֶר וּפִשְׁתִּ֖ים יַחְדָּֽו׃
(יב) גְּדִלִ֖ים תַּעֲשֶׂה־לָּ֑ךְ עַל־אַרְבַּ֛ע כַּנְפ֥וֹת כְּסוּתְךָ֖ אֲשֶׁ֥ר תְּכַסֶּה־בָּֽהּ׃ (ס)
(9)
You are not to sow your vineyard with two kinds,
lest you forfeit-as-holy the full-yield from the seed that you sow
and the produce of the vineyard.
(10) You are not to plow with an ox and a donkey together.
(11) You are not to clothe yourself in shaatnez, wool and flax together.
(12) Twisted-cords you are to make yourself on the four corners of your tunic-covering with which you cover yourself.
JPS
9. You shall not sow your vineyard with a second kind of seed, else the crop-from the seed you have sown- and the yield of the vineyard not be used.
10. You shall not plow with an ox and an ass together.
11. You shall not wear cloth combining wool and linen.
12. You shall make tassels on the four corners of the garment with which you cover yourself.
Leviticus 19:19
You shall observe my decrees: you shall not mate your animal into another species, you shall not plan your field with mixed seed; and a garnet that is a mixture of combined fibers shall not come upon you.
RASHI...The prohibitions not to crossbreed or to wear mixtures of wool and linen are the quintessential chukim (decrees), i.e. commands of the King for which man knowns no reason.
RAMBAN...God surely has reasons, but since man cannot know them, he cannot feel the same satisfaction in performing these decrees that he has when he performs precepts that he feels he understands. God created the world with certain distinct species, and His wisdom decreed that these species remain intact and unadulterated. For man to take it upon himself to alter the order of Creation suggests a lack of faith in God's plan. Moreover, each species on earth is directed by a Heavenly force, so that the earthly species represent profound spiritual forces. To tamper with them is to cause harm that earth bound humans cannot fathom.
9.
RAMBAN...כִּלְאָ֑יִם...A mixture...To the prohibition already given in Leviticus 19:19 , the Torah adds that all possible benefits from the growth of such planting are forbidden.
PLAUT...this reflects the biblical aversion to interfering with the established order of nature- in stark contrast with the objectives of modern technology.
10.
RASHI... בְּשׁוֹר־וּבַחֲמֹ֖ר...An ox and a donkey. The prohibition applies not only to oxen and donkeys, or to plowing, but to any coupling of two different speices, for any kind of work.
JPS...The present law protects draught animals. Since the ox and the ass are of unequal strength, if they were yoked together the stronger one might exhaust the weaker, or one might cause the other to stumble and be injured.
11.
JPS...This prohibition cannot be viewed as protecting the distinction between species. It does not prohibit combining wool and linen, but only wearing a cloth made from that combination. The rabbis could think of no explanation for this prohibition....[however] Josephus's conjecture is probably correct: the prohibition applies to the laity, because the priests, when they officiate, do wear garments made of such mixtures. The status of such garments is thus comparable to that of the sacred anointing oil and the incense that is used in the sanctuary and may not be made or used by laypersons, as stated in Exodus 30:22-37.
12.
ARTSCROLL....Tzitzis...The juxtaposition of this positive commandment with the prohibition against shaatnez shows the general rule that a positive commandment supersedes a negative commandment. Thus, in the case of a linen garment, the commandment to insert tzitzis, with the required turquoise woolen thread (techelet), overrides the prohibition against mixing wool and linen. (Yevamot 4a). Therefore, if techelet is available, it is permitted to put woolen fringes in a linen garment.