2 Chronicles 29:36

And Hezekiah rejoiced, and all the people, that God had prepared the people: for the thing was done suddenly.

The rejoicing came at the first service held in the cleansed temple, when the rulers of the city united with the king, the priests, and the Levites in seeking forgiveness for the sins of the nation. Sin offerings were presented that made atonement for all Israel, and the king and all who were present bowed in worship. Hezekiah and all the people rejoiced because God had prepared the people, making their hearts ready to take part in restoring the temple worship and in reforming Judah. They rejoiced also because the work of restoration had been done suddenly and completed quickly.

Their joy filled the temple courts again with praise and adoration. The songs of David and of Asaph were sung with gladness. The worshipers sang in this way because they understood that they were being set free from slavery to sin and from turning away from God.