3,913. Not Performing Someone Else's Job

Hilchos Klei HaMikdash 3:10

Just as the Leviim were warned against performing the job of the kohanim, the kohanim were warned not to perform the job of the Leviim. Numbers 18:3 (cited in the previous halacha) says, “Neither they (the Leviim), nor you (the kohanim).” The Leviim were likewise warned not to perform a job assigned to a fellow, i.e., a singer may not assist a gatekeeper, nor vice versa. Numbers 4:49 teaches: “Each man according to his service and his burden.”

Hilchos Klei HaMikdash 3:11

If a Levi performs the job of a kohein, or if a Levi assists in a job that he wasn’t assigned, he is subject to the penalty of death at the hands of heaven. This is as per Numbers 18:3: “so they will not die.” However, if a kohein performs the job of a Levi, he isn’t subject to heavenly death. Rather, he violates a prohibition.