No Levite must do another's work of either a Kohen or a Levite

This mitzvah prohibits blurring the distinct roles of Kohanim and Levites in the Mikdash. A Levite may not approach the altar or perform priestly sacrifices, while a Kohen may not assume Levite responsibilities such as guarding, carrying, or singing. Each tribe was sanctified with a unique role, and violating these boundaries desecrates Hashem’s service.

Rambam explains that these roles were divinely designated: the Kohanim descended from Aharon to serve as officiants of the sacrifices, while the Levites were assigned as assistants and guardians. The Torah insists that one not overstep into the role of the other, ensuring order and sanctity in the Temple service.

The Sefer HaChinuch teaches that this separation instills awe and discipline, preventing confusion and preserving honor for each tribe’s duties. The Talmud teaches that if either Kohen or Levite crosses these lines, the act is punishable and treated as a grave violation.

Commentary & Classical Explanation:

• Rambam (Hilchot Klei HaMikdash 3:10): States explicitly that a Kohen may not perform Levite service, nor a Levite Kohanic service.
• Sefer HaChinuch (Mitzvah 390): Explains that Hashem assigned distinct roles to maintain sanctity and order in the Mikdash.
• Rashi (Num. 18:3): Notes that Levites may not draw near the altar or the sacred vessels of the Kohanim.
• Talmud (Sanhedrin 83a): Rules that a Levite who performs priestly service or a Kohen who takes on Levite work is liable for punishment.
• Ramban (Num. 18:7): Emphasizes that mixing these roles undermines Hashem’s sanctification of each tribe’s unique duties.