Leviticus 19:19

Prohibition of improper mixtures. Apparently the precept was based upon the view that each individual, animate or inanimate, had individual qualities assigned by the Creator, and that to mix them was therefore directed against God's ordinance, and as such involved impurity. Cp. Deuteronomy 22:5; Deuteronomy 22:9-11, where the prohibition is extended to the wearing by one sex of garments properly belonging to the other, or the attaching of an ox and an ass to the same plough.