וְאַל־יָב֣וֹא בֵית־יְהוָ֗ה כִּ֤י אִם־הַכֹּֽהֲנִים֙ וְהַמְשָׁרְתִ֣ים לַלְוִיִּ֔ם הֵ֥מָּה יָבֹ֖אוּ כִּי־קֹ֣דֶשׁ הֵ֑מָּה וְכָל־הָעָ֔ם יִשְׁמְר֖וּ מִשְׁמֶ֥רֶת יְהוָֽה׃
But let none come into the house of the LORD, save the priests, and they that minister of the Levites; they shall come in, for they are holy; but all the people shall keep the charge of the LORD.
Read midrashic interpretation of II Chronicles 23:6: and classical rabbinic exegesis.