Leviticus 19:19 and Deuteronomy 22:11 are in effect a consumer protection law, built on the principle that materials of widely differing character and texture are not to be combined. Natural fibers fall into two kinds: plant cellulose fibers such as linen and cotton, and animal protein fibers such as wool and silk. These two kinds differ markedly in strength, washability, and absorption, so they should not be mixed. Mixtures within a kind are acceptable, such as cotton with linen or wool with mohair and silk, because the fibers are basically similar. Synthetics such as Dacron, nylon, polyester, and rayon do not necessarily break the principle either, since they are made to share the characteristics of natural fibers and must be compatible or the stronger fibers would tear away from the weaker. What matters is that fibers with markedly differing qualities are not combined. Blends usually make a cheaper garment than the best pure fibers, though a low-grade natural fabric is often improved by compatible man-made fibers. Clothing of lower quality or a wrong mixture need not be thrown away, and wearing it is not a sin. God does not want manufacturers producing shoddy goods to take advantage of customers. The wise course is to buy the best quality one can afford, since it lasts longer and fits better, and to honor God in what is worn, especially to church services, without going into debt.

The directive against wearing garments of mixed materials, specifically wool and linen together, is found in Deuteronomy 22:11 and Leviticus 19:19. This law, known as sha'atnez in Hebrew, meaning mixed stuff, focuses on the prohibition of combining these two fabrics in a single garment. The principle behind this edict may point to separation, reflecting how God desired the physical nation of Israel to remain distinct from surrounding nations. Spiritually, this principle of separation continues to apply, urging believers to maintain purity and avoid entanglement with sin. While adhering to this specific clothing restriction may not be binding under the New Covenant, the underlying call to be set apart as God's special people remains significant, emphasizing a life dedicated to spiritual purity and distinction from worldly influences.

In examining the principles by which we discern the applicability of certain laws, we find specific guidance concerning the mixing of materials in clothing. The law regarding linen and wool illustrates a broader intent beyond its literal application. It specifically prohibits mixing fibers from a vegetable product and an animal product into the same piece of material. However, the spirit of this law expands to a practical application, teaching us to avoid poor quality by not mixing animal and vegetable fibers. The intent is to purchase the best quality one can afford, showing that this principle still holds relevance in guiding our choices.