Boyd’s Bible Dictionary:
A highly prized material for clothing among Hebrews
(Lev. 13:47; Job 31:20; Prov. 31:13; Ezek. 27:18; 34:3). Mixed woolen and linen fabrics forbidden (Lev. 19:19; Deut. 22:11).
Concise Bible Dictionary:
Wool
The fleece of sheep and other animals. That of sheep was used for weaving into cloth, and is generally referred to as “wool.” In the figurative language of Isaiah 1:18 undyed wool represents the state resulting from the removal of sin by Jehovah from His people; the sin being compared to that which had been dyed crimson. The law forbade the wearing of a garment made of linen and wool: it was an unnatural mixture, figurative of the working of the Spirit and the flesh in a Christian (Lev. 19:19; Deut. 22:11).