Answer
Two passages in the Mosaic Law forbid wearing clothing made of different types of fabric; that is, blended fabrics—those woven from two different materials.
Both passages address three different types of “blending”:
Leviticus 19:19: “Keep my decrees. Do not mate different kinds of animals. Do not plant your field with two kinds of seed. Do not wear clothing woven of two kinds of material.”
Deuteronomy 22:9–11: “Do not plant two kinds of seed in your vineyard; if you do, not only the crops you plant but also the fruit of the vineyard will be defiled. Do not plow with an ox and a donkey yoked together. Do not wear clothes of wool and linen woven together.”
The Deuteronomy passage is more specific in its rule against wearing a wool-and-linen weave. The Leviticus passage gives the broader prohibition, forbidding clothes woven of two different types of fabric. Leviticus does not specify what material is used. Wool and linen would have been the primary options for the ancient Israelite when making thread for weaving. Wool is animal-based. In Moses’ day, woolen thread would have been made from the hair of a sheep or goat (today it is made from a variety of other animals, too, such as llamas and alpacas). Linen is plant-based and was made from the flax plant (see Joshua 2:6). There is no evidence that ancient Israel cultivated cotton, and they did not have synthetics like nylon or polyester.Deuteronomy 22:9–11: “Do not plant two kinds of seed in your vineyard; if you do, not only the crops you plant but also the fruit of the vineyard will be defiled. Do not plow with an ox and a donkey yoked together. Do not wear clothes of wool and linen woven together.”
Neither passage says anything about wearing two different garments made of different kinds of material. So, a linen undergarment worn with a woolen outer garment may have been acceptable. Nor do the commandments say anything about clothing that is not woven, such as leather or animal skins, being sewn to a lining made of wool or linen. The law’s prohibition pertained only to wearing a single garment woven with both wool and linen.
The rule against wearing different types of fabric was not a moral law but a ceremonial one. There is nothing inherently wrong with weaving linen and wool together.
The passages forbidding wearing clothes woven with wool and linen include other prohibitions against improper combinations: mixing different animals and mixing different seeds. We don’t know the exact reasons these rules were in place, but we can assume the ancient Israelites knew.
The laws against improper mixtures may have been designed to keep the Israelites from imitating the superstitious practices of the nations surrounding them. For example, the practice of wearing clothing made of different types of fabric could have been common in the religion of idolators, and God did not want His people imitating such things. Or the reason could have been to remind the Israelites of their responsibility to be separate and holy. God wants religion to be “pure and undefiled” (James 1:27, ESV). The Mosaic Law required singlemindedness, simplicity, and purity to extend to all that God’s people touched.
Is it wrong for a Christian today to wear clothing made of two different types of material? The clear and unequivocal answer is “no.” The prohibition against blended fabric was for ancient Israel living under the law, not for the New Testament Christian in the age of grace. The ceremonial laws for ancient Israel as recorded in the Old Testament simply do not apply today.