390. Also Sprach Zar: The prohibition against a non-kohein serving

A kohein is a direct, patrilineal descendant of Moses’ brother Aaron, A zar (“outsider”) is any non-kohein. A zar is prohibited from doing any work of a kohein. The work of the kohein includes every step of the sacrificial process from the gathering of the blood and on. Other tasks – such as slaughtering a sacrifice – were not specific to the kohanim and could be performed by others.

The reason for this prohibition is that it is an honor to God to have certain, appointed people ministering in the Temple. A king wouldn’t have just any random volunteer show up to serve him. All the more so, only those selected by God and specially trained in His service should officiate in the Temple.

This mitzvah applies to both men and women in Temple times. In the Talmud, it is discussed in tractate Zevachim, starting on page 15b, in Yoma on 24a-b and, passingly, in tractate Sanhedrin on page 81b. It is codified in the Mishneh Torah in the ninth chapter of Hilchos Bi’as HaMikdash. This mitzvah is #74 of the 365 negative mitzvos in the Rambam’s Sefer HaMitzvos.