Exod 25:4

“It is very necessary that when we are moved by compunction concerning ourselves, we also be zealous for the life of those entrusted to us. Therefore, let the bitterness of compunction affect us in such a way that it does not turn us away from the care of our neighbors. For what does it profit if, loving ourselves, we abandon our neighbors? Or again, what does it profit if, loving or being zealous for our neighbors, we abandon ourselves? Indeed, in the adornment of the tabernacle, twice-dyed scarlet is commanded to be offered, so that before the eyes of God our charity may be colored with love of God and neighbor. But he truly loves himself who purely loves his Creator. Therefore, the scarlet is dyed twice when the soul is inflamed with love of truth toward both itself and its neighbor.”

“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). וארגמן AND RED PURPLE — wool coloured with a kind of dye the name of which is ארגמן ושש — this is what we call LINEN (Yevamot 4b). ועזים is GOATS’ HAIR; therefore Onkelos translates it by וּמְעַזֵּי which denotes something that comes from the goats — not the goats themselves, for the Aramaic translation of עזים is עִזַּיָּא‎.”

“Scarlet twice dyed. Aquila and Symmachus have transparent. This colour is often confounded with purple, as our Saviour’s robe is styled scarlet by St. Matthew xxvii. 28, and purple by St. John xix. 2. It was dyed with a worm called shani in Hebrew. (St. Jerome, ep. ad Fabiol.) — Fine linen, byssus. Hebrew shésh, “of six folds,” or it may mean cotton, which was highly esteemed by the ancients; (Arabic version; Herodotus) and it is not probable that Moses would have passed over it unnoticed. (Calmet)”