דברי הימים א, פרק כ״ג, פסוק כ״ו

The establishment of a permanent spiritual center in Jerusalem brought about a fundamental shift in the duties of the Levites. After generations of wandering, the nature of their holy work changed completely. The primary approach among commentators is that the Levites were no longer required to carry the Tabernacle and its vessels on their shoulders from place to place, as they had done in the desert. This transition occurred because the sanctuary of God had finally reached its resting place, standing permanently in Jerusalem.

The end of this heavy physical labor led to a practical adjustment in the requirements for their service. Because their duties now focused mainly on singing, they no longer needed to wait until the age of thirty to begin serving. Carrying heavy loads demanded the peak physical strength of a thirty-year-old man, but for roles centered on song, younger Levites were fully capable of serving starting at the age of twenty [מצודת דוד]. Furthermore, their ongoing responsibilities involved caring for the specific vessels that were crafted and designated exclusively for the service of the Tabernacle [מצודת דוד].