נחמיה, פרק י״ב, פסוק מ״ה

The priests and Levites carried out their sacred duties with a dedication that brought great joy to the people of Judah [מצודת דוד]. Their responsibilities centered on a deep commitment to the service of God that was entrusted to them [מצודת דוד, ביאור שטיינזלץ], which some understand to include the actual physical guarding of the Temple [רלב״ג].

Alongside these tasks, they maintained a strict watch over the purity of the sanctuary. They carefully monitored the grounds to ensure that nothing unclean could enter and defile the holy space [רלב״ג, מצודת דוד, ביאור שטיינזלץ]. The singers and gatekeepers also remained steadfast at their posts, faithfully carrying out their assigned roles [מצודת דוד, ביאור שטיינזלץ].

This entire system of shifts and responsibilities was upheld exactly as David had originally commanded his son Solomon, following the precise arrangements recorded in the Book of Chronicles [מצודת דוד].