No Levite must do the work of either another priest or another Levite

"And they shall thus attend to your obligation and the obligation of all the tent, but they shall not come near to the furnishings of the sanctuary and the altar, or both they and you will die.

Hebrew

ג וְשָׁמְרוּ, מִשְׁמַרְתְּךָ, וּמִשְׁמֶרֶת, כָּל-הָאֹהֶל: אַךְ אֶל-כְּלֵי הַקֹּדֶשׁ וְאֶל-הַמִּזְבֵּחַ לֹא יִקְרָבוּ, וְלֹא-יָמֻתוּ גַם-הֵם גַּם-אַתֶּם.

Greek

3 καὶ φυλάξονται τὰς φυλακάς σου καὶ τὰς φυλακὰς τῆς σκηνῆς, πλὴν πρὸς τὰ σκεύη τὰ ἅγια καὶ πρὸς τὸ θυσιαστήριον οὐ προσελεύσονται, καὶ οὐκ ἀποθανοῦνται καὶ οὗτοι καὶ ὑμεῖς.

• Parashah: Korach
• Sefer HaChinuch: 389
• Mishneh Torah: Service — The Vessels of the Temple and Those Who Serve in It

• Numbers 18:3

Enumeration and classification from BibleData. The Greek is the Septuagint reading of the same verse, carried by the source for comparison.