Read: Leviticus 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. Lev 19:19
How many of you are observing that last law? Almost all garments today are made of mixed stuff, of blends of natural and synthetic fibers. A literal adherence to this stricture is no longer of any significance, because it is dealing with substances which never were inherently wrong. Whenever God employs things symbolically and says that something connected with them is wrong, they are no longer tended to be taken literally but are meant to illustrate attitudes of mind and heart which are dangerous. The Israelites had to obey these literally, because that is how they learned what these attitudes were. But we need to understand that God is teaching in a graphic way here that there are certain unmixable principles which are unalterably opposed to one another and that we are not to try to put the two together.