Why did God say not to mingle linen and wool? What does this mean for us today?
In addition to His eternal spiritual commandments, God gave Israel various statutes and judgments as part of its civil code or national law. Most aren't binding laws for Christians today, but Christians should consider and learn from the principles contained in all of them. Is there any principle in these laws or in their intended purpose that can guide Christians in everyday life?
In its introductory notes on Leviticus, Expositor's Bible Dictionary points out: "The weaving of two kinds of material (wool and linen in Deuteronomy:22:11) may be a rule that would prevent loss by unequal shrinkage." There is no apparent application today for two reasons: (1) Most Christians do not make their own fabric or clothing today, and (2) clothing manufacturers do not mix these materials.
However, the broader principle of the several statutes that forbid "mixing" in various ways is that God wanted His people to pursue purity and quality. Similarly, Christians are to pursue pure and godly character. The Jamieson, Fausset and Brown Commentary offers the following explanation for Leviticus:19:19:
"Neither shall a garment mingled of linen and woollen come upon thee—Although this precept, like the other two with which it is associated, was in all probability designed to root out some superstition, it seems to have had a farther meaning. The law, it is to be observed, did not prohibit the Israelites wearing many different kinds of cloths together, but only the two specified; and the observations and researches of modern science have proved that 'wool, when combined with linen, increases its power of passing off the electricity from the body. In hot climates, it brings on malignant fevers and exhausts the strength; and when passing off from the body, it meets with the heated air, inflames and excoriates like a blister' [Whitlaw]. (See Ezek:44:17, 18.)"