We have here busy work, good work, and needful work, the cleansing of the house of the Lord.
I. The persons employed in this work were the priests and Levites, who should have kept the temple clean, but, not having done that, were concerned to make it clean. Several of the Levites are here named, two of each of the three principal houses, Kohath, Gershon, and Merari (Ch2 29:12), and two of each of the three families of singers, Asaph, Heman, and Jeduthun, Ch2 29:13, Ch2 29:14. We cannot think these are named merely because they were chief in place (for then surely the high priest, or some of the heads of the courses of the priests, would have been mentioned), but because they were more zealous and active than the rest. When God has work to do he will raise up leading men to preside in it. And it is not always that the first in place and rank are most fit for service or most forward to it. These Levites not only bestirred themselves, but gathered their brethren, and quickened them to do according to the commandment of the king by the word of the Lord. Observe, They did according to the king's command, but with an eye to God's word. The king commanded them what was already their duty by the word of God, and, in doing it, they regarded God's word as a rule to them and the king's commandment as a spur to them.
II. The work was cleansing the house of God, 1. From the common dirt it had contracted while it was shut up - dust, and cobwebs, and the rust of the vessels. 2. From the idols and idolatrous altars that were set up in it, which, though kept ever so neat, were a greater pollution to it than if it had been made the common sewer of the city. The priests were none of them mentioned as leading men in this work, yet none but they durst go into the inner part of the house, no, not to cleanse it, which they did, and perhaps the high priest into the holy of holies, to cleanse that. And, though the Levites had the honour to be the leaders in the work, they did not disdain to be servitors to the priests according to their office; for what filth the priests brought into the court the Levites carried to the brook Kidron. Let not men's usefulness, be it ever so eminent, make them forget their place.
III. The expedition with which they did this work was very remarkable. They began on the first day of the first month, a happy beginning of the new-year, and one that promised a good year. Thus should every year begin with the reformation of what is amiss, and the purging away, by true repentance, of all the defilements contracted the foregoing year. In eight days they cleared and cleansed the temple, and in eight days more the courts of the temple, Ch2 29:17. Let those that do good work learn to rid work and get it done. Let what is amiss be amended quickly.
IV. The report they made of it to Hezekiah was very agreeable, Ch2 29:18, Ch2 29:19. They gave him an account of what they had done, because it was he that set them on work, boasted not of their own care and pains, nor did they come to him to be paid, but to let him know that all things that had been profaned were now sanctified according to law, and were ready to be used again whenever he pleased. They knew the good king had set his heart upon God's altar, and longed to be attending that, and therefore they insisted most upon the readiness they had put that into - that the vessels for the altar were scoured and brightened. Those vessels which Ahaz, in his transgression, had cast away as vessels in which there was no pleasure, they gathered together, sanctified them, and laid them in their place before the altar. Though the vessels of the sanctuary may be profaned for a while, God will find a time and a way to sanctify them. Neither his ordinances nor his people shall be suffered to fail for ever.

And the priests went - The priests and Levites cleansed first the courts both of the priests and of the people. On this labor they spent eight days. Then they cleansed the interior of the temple; but as the Levites had no right to enter the temple, the priests carried all the dirt and rubbish to the porch, whence they were collected by the Levites, carried away, and cast into the brook Kidron; in this work eight days more were occupied, and thus the temple was purified in sixteen days.

Then they went in to Hezekiah the king,.... In his palace:

and said, we have cleansed all the house of the Lord; the several parts of it, and apartments belonging to it:

and the altar of burnt offering, with all the vessels thereof; which they cleansed and scoured, and put in their proper place, and which Ahaz had removed:

and the shewbread table, with all the vessels thereof; which had lain neglected and profaned, but were now put in order.

THE HOUSE OF GOD CLEANSED. (2Ch. 29:12-36)

Then the Levites arose--Fourteen chiefs undertook the duty of collecting and preparing their brethren for the important work of cleansing the Lord's house. Beginning with the outer courts--that of the priests and that of the people--the cleansing of these occupied eight days, after which they set themselves to purify the interior; but as the Levites were not allowed to enter within the walls of the temple, the priest brought all the sweepings out to the porch, where they were received by the Levites and thrown into the brook Kedron. This took eight days more. At the end of this period they repaired to the palace and announced that not only had the whole of the sacred edifice, within and without, undergone a thorough purification, but all the vessels which the late king had taken away and applied to a common use in his palace, had been restored, "and sanctified."