2 Chr 35:15

וְהַמְשֹֽׁרֲרִ֨ים בְּנֵי־אָסָ֜ף עַל־מַעֲמָדָ֗ם כְּמִצְוַ֤ת דָּוִיד֙ וְאָסָ֞ף וְהֵימָ֤ן וִֽידֻתוּן֙ חוֹזֵ֣ה הַמֶּ֔לֶךְ וְהַשֹּׁעֲרִ֖ים לְשַׁ֣עַר וָשָׁ֑עַר אֵ֣ין לָהֶ֗ם לָסוּר֙ מֵעַ֣ל עֲבֹֽדָתָ֔ם כִּֽי־אֲחֵיהֶ֥ם הַלְוִיִּ֖ם הֵכִ֥ינוּ לָהֶֽם׃

The singers, the descendants of Asaph, were at their stations according to the command of David, Asaph, Heman, and Jeduthun the king’s seer. And the gatekeepers at each gate did not need to leave their position, because their fellow Levites made preparations for them.