Tafsiran Ulangan 22:11: Rashi, Chizkuni, Da'at Zekenim & Tur HaArokh

שעטנז is an expression for a mixture. Our Rabbis explained it to mean a material that is calendered (pressed, שוע), or woven (טווי), or twisted (נוז) together (Sifrei Devarim 232:1); (שעטנז is taken to be an abbreviation of these words; cf. Rashi on Leviticus 19:19 and our Note thereon).

צמר ופשתים יחדו, “wool and linen together.” The reason why only these two categories of yarns are forbidden to be mixed is that the two were involved in the first murder. Kayin’s offering to G-d had consisted of leftover flax that he had grown, while Hevel had offered sheep which grow wool. Seeing that these two species had been indirectly responsible for the first disagreement between two human beings ending in the death of one, we are to be forever mindful of this. An alternate interpretation: These two fibers were used in the garments worn by the priests when performing service in the Temple but are not permitted to be worn by the priests at any other times. This is why the affliction known as tzoraat, does not strike garments consisting of any other fibers. This is a reminder that there is a basic problem involving these fibers, one that is overcome only on holy consecrated ground when used by the priests in their service to G-d. The Torah teaches that the expression shatnes, means a mixture of woolen and flax (linen) fibers.

לא תלבש שעטנז, “do not wear a garment consisting of wool and linen intertwined.” The reason for this prohibition is that the dividing curtain in the Temple was made of a mixture of fine linen and wool dyed blue. G–d did not want Jews to wear something symbolising that dividing curtain behind which was the Holy Ark from the lid of which the voice of G–d could be heard. (by Moses) The same warning not to duplicate such sacred combinations was issued to the people in connection with the ingredients and quantities of the spices in the k’toret, incense to be offered up twice daily. (Compare Exodus 30,38, and the Talmud in tractate Rosh Hashanah folio 24) People are also not to build annexes to their houses by duplicating measurements used for the Temple. An alternate reason offered for this prohibition of mixing wool and linen, is that Kayin’s offering consisted of linen, and Hevel’s of wool, and is therefore a reminder of jealousy and hatred, the opposite of what the Torah stands for.