Any place where an imperative expression begins with the word זה (this), it is proper for the imperative verb to come without the word אשר. Like זה תאכלו..וזה לא תאכלו (This you may eat…And this you may not eat). And if the word אשר does come, like זאת החיה אשר תאכלו (these are the living things which you may eat)⁷⁵⁹, it teaches that the imperative already preceded it in a general way, and it is coming to clarify the imperative.

footnotes: ⁷⁵⁹ Leviticus 11:2.