Wool

Concise Bible Dictionary:

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 1:1818Come now, and let us reason together, saith the Lord: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool. (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. 19:1919Ye shall keep my statutes. Thou shalt not let thy cattle gender with a diverse kind: thou shalt not sow thy field with mingled seed: neither shall a garment mingled of linen and woollen come upon thee. (Leviticus 19:19); Deut. 22:1111Thou shalt not wear a garment of divers sorts, as of woollen and linen together. (Deuteronomy 22:11)).