דברי הימים א, פרק ט״ז, פסוק ד׳

Long before the permanent Temple was built, King David took deliberate steps to ensure a structured and dignified service around the Ark of the Covenant. While the primary altar for sacrifices was located in Gibeon under the leadership of Heman, David established a constant presence of priests and Levites around the holy tent where the Ark rested, placing them under the direction of Asaph [רלב״ג, ביאור שטיינזלץ].

The Levites assigned to the Ark were given both practical and spiritual responsibilities. Their first duty was physical maintenance. They served as a permanent staff dedicated to cleaning, sweeping, and preparing the ground before the Ark, ensuring the space maintained an atmosphere of absolute dignity and respect [מצודת דוד, מלבי״ם, ביאור שטיינזלץ].

Alongside this physical upkeep, the Levites were tasked with a complex musical service performed with both their voices and instruments. This spiritual duty was divided into three distinct expressions. First, they were instructed to invoke or remind. This involved singing songs that either brought the Israelites to God's attention or recounted His great historical deeds from ancient times [מלבי״ם, ביאור שטיינזלץ]. Others understand this as a precise instruction to recite specific Psalms that feature a corresponding title [רש״י].

The second part of their musical service was to offer thanks, expressing deep gratitude for God's goodness [מלבי״ם], which practically meant reading Psalms that open with a call to give thanks to Him [רש״י]. Finally, they were commanded to praise, actively telling of God's greatness [מלבי״ם] by singing the specific Psalms that begin with the word Hallelujah [רש״י].