Boyd’s Bible Dictionary:
(flax). Used for stately robes (Gen. 41:42); priestly vestments (Ex. 28:42; Lev. 6:10); temple veil (2 Chron. 3:14); choral gowns (2 Chron. 5:12), and ordinary dress. Symbol of purity (Rev. 15:6); of luxury (Luke 16:19).
Concise Bible Dictionary:
Linen
Various Hebrew and Greek words are translated “linen,” and there can be no doubt that linen made of flax was known in ancient Egypt and to the Israelites; but cloths generally are called “linen” whether made of cotton or flax, some being distinguished as “fine linen,” such as was worn by the priests, kings. The word shesh, often translated “fine linen” and “fine twined linen” (for the curtains of the tabernacle, etc.) signifies “whiteness,” and is applicable to both fine linen and cotton (Ex. 26:1,31). Joseph was arrayed in “vestures of fine linen” (Gen. 41:42). The wrappings on the ancient Egyptian mummies were for a long time judged to be cotton, but by the use of the microscope they have been discovered to be linen.