(Devarim 22:9) "You shall not sow your vineyard with mixed seed": [I might think that he may not sow one (variety) by itself and another by itself; it is, therefore, written "kilayim" (mixed seed), but each by itself is permitted. Variantly:] "kilayim": Why is this needed? Is it not already written (Vayikra 19:19) "You shall not sow your field kilayim"? To impose liability for both "vineyard" and "field." We are hereby taught that one who sows kilayim in a vineyard transgresses two negative commandments.