Comentário sobre Êxodo 25:4

ותכלת AND BLUE PURPLE — wool dyed with the blood of the חלזון (a kind of shell-fish), the colour of which was greenish-blue (Menachot 44a).

ותולעת שני, wool dyed red is called תולעת. The colour itself is called שני. We know this from Nachum 2,4 אנשי חיל מתולעים, “soldiers dressed in crimson.” The word also occurs in that sense in Lamentations 4,5 האמונים עלי תולע, “the ones who used to be robed in purple, etc.” The prophet Isaiah 1,18 holds out the hope that “if our sins were staining our clothing red, repentance would result in their becoming white as snow.” The prophet considers both the word שלג and שני as dyes, the former being a white dye, the latter a red dye. However the words תולע and צמר both refer to wool, the latter being undyed wool.

Wool that is dyed with the blood. . . Rashi explains ארגמן , too, as dyed wool. His proof is from the priestly vestments, which were made of these four types — תכלת , ארגמן , תולעת שני , ושש — yet in Scripture it is not written what material they were. But in Yechezkel 44:17, regarding the kohanim’s garb on Yom Kippur, it is written: “They shall wear vestments of linen, and vestments of wool shall not come upon them.” This implies that during the year they wore linen and wool vestments, but no other material. About the kohanim’s pants it is written (39:28): ואת מכנסי הבד שש משזר . Since בד is linen, שש is linen. And if שש is linen, then תכלת must be wool, [because the kohanim wore only linen and wool]. It cannot be the other way around because we see clearly that שש is linen. And since תכלת of the priestly vestments is [dyed] wool, also ארגמן [and תולעת שני ] must be types of dyed wool, [as all the dyed types were assumedly of the same material. But שש was not dyed].