And you shall give it to Elazar the Kohen, and he shall take it outside the camp and slaughter it before him.
Torah Temimah: Chullin 24a — By shechitah it is valid; by arifah it is invalid. Why? Because the verse says “veshachat” and “chukah” is written; by shechitah yes, by arifah no.
English: By shechitah it is valid; by arifah it is invalid. What is the reason? Because the verse says “veshachat” and “chukah” is written; by shechitah yes, by arifah no.
Chukah language limiting the method of killing to proper shechitah.
The para aduma must be killed by proper shechitah; killing it by arifah (breaking the neck) renders it invalid.