Deuteronomy 22:9-11
Illustrations of the Principle of Purity
22:9 You must not plant your vineyard with two kinds of seed; otherwise the entire yield, both of the seed you plant and the produce of the vineyard, will be defiled.
22:10 You must not plow with an ox and a donkey harnessed together.
22:11 You must not wear clothing made with wool and linen meshed together.