The duty of the Levites was to help Aaron’s descendants in the service of the temple of the Lord

1 Chronicles 23:1-32
The Levites thirty years old or more were counted, and the total number of men was thirty-eight thousand. David said, “Of these, twenty-four thousand are to be in charge of the work of the temple of the Lord and six thousand are to be officials and judges. Four thousand are to be gatekeepers and four thousand are to praise the Lord with the musical instruments I have provided for that purpose.”
The duty of the Levites was to help Aaron’s descendants in the service of the temple of the Lord: to be in charge of the courtyards, the side rooms, the purification of all sacred things and the performance of other duties at the house of God. They were in charge of the bread set out on the table, the special flour for the grain offerings, the thin loaves made without yeast, the baking and the mixing, and all measurements of quantity and size. They were also to stand every morning to thank and praise the Lord. They were to do the same in the evening and whenever burnt offerings were presented to the Lord on the Sabbaths, at the New Moon feasts and at the appointed festivals. 
The next five chapters record David's organization of the nation's religious and civil administration.
From the earliest days of desert wandering, the job of the Levites had been the care and transport of the Tabernacle. They had also served the priests - in later times at the many shrines scattered throughout the land. Now the Ark was to have a permanent home, and worship was to be centralized in the Temple at Jerusalem. So David allocates new duties to the Levites: the care0taking and maintenance of the Temple; appoints as magistrates, janitors, musicians of the priests.
Why?
David made the new jobs in the Temple for there was no duty to remove the tent of the Lord to other places. Jerusalem is the worship center and God is with them forever.
Worship the Lord is daily regulation, and serve the Lord is the daily job to Levites. So as Christian to worship God and serve the Lord every day.
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聖殿只是硬體，更重要是裏面的服事人員。預備人員。
比材料描述，用更長的篇幅記載，表示更重要。
不用再搬運幕了，敬拜、唱詩的工作也指派了。分工清楚。
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How?
Worship with all of my heart, my mind, and my strength every day.