נחמיה, פרק י״ב, פסוק ט׳

The service of the Levites operated with perfect order, carefully organized into parallel groups. Bakbukiah, Unni [מנחת שי], and their men stood directly opposite their fellow Levites, specifically the associates of Mattaniah [מצודת דוד]. They were positioned to face one another, reflecting an equal status and an identical group structure [מצודת דוד, ביאור שטיינזלץ].

This careful arrangement was based on a system of rotating shifts. It mirrored the traditional structure in which the Levites were organized into twenty-four distinct groups to carry out their daily work [רש״י].