Halakhah for Zevachim 227:2

From the laws of the commandment is that which they, may their memory be blessed, said that this warning of approaching is only [about] one who approaches to [do] a service from one of the services that are specific to a priest. And it is like they, may their memory be blessed, said (Zevachim 32a), “From the receiving of the blood and onward, it is a commandment of the priesthood.” For example, pourings, mixings, wavings, bringings and many other services like these that are explained in the Gemara that are commanded to be with a priest; behold, they are all with a warning to the foreigner, and the [effected] sacrifice is disqualified. But there are [also] services that are not included in this warning, such as slaughtering, which is fit, even a priori, with a foreigner, and even of sacrifices of the highest sanctity. And so [too,] lighting the lights; such that if a priest took them outside after he arranged them, it is permitted for a foreigner to light them. And there are only four specific services among them that are weighty, such that there is liability for the death penalty for them. And they are throwing, burning incense, placement [of the sacrifice] and pouring libations. And it is about them that it is stated, “and the foreigner that approaches shall die,” as it is elucidated in the first chapter of Yoma [entitled] Kol Mi Shehu Rotseh Litrom (Yoma 24a). [This] and the rest of its details are elucidated there in Yoma and in the last chapter of Tractate Zevachim. (See Mishneh Torah, Laws of Admission into the Sanctuary 3.)