2 Chronicles 30:21
“And the children of Israel that were present at Jerusalem kept the feast of unleavened bread seven days with great gladness: and the Levites and the priests praised the Lord day by day, singing with loud instruments unto the Lord.”
That prepareth his heart to seek God, the Lord God of his fathers, though he be not cleansed according to the purification of the sanctuary.
And the Lord hearkened to Hezekiah, and healed the people.
And the children of Israel that were present at Jerusalem kept the feast of unleavened bread seven days with great gladness: and the Levites and the priests praised the Lord day by day, singing with loud instruments unto the Lord.
And Hezekiah spake comfortably unto all the Levites that taught the good knowledge of the Lord: and they did eat throughout the feast seven days, offering peace offerings, and making confession to the Lord God of their fathers.
And the whole assembly took counsel to keep other seven days: and they kept other seven days with gladness.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“And kept the feast of unleavened bread seven days with joy: for the Lord had made them joyful, and turned the heart of the king of Assyria unto them, to strengthen their hands in the work of the house of God, the God of Israel.”
“And now shall mine head be lifted up above mine enemies round about me: therefore will I offer in his tabernacle sacrifices of joy; I will sing, yea, I will sing praises unto the Lord.”
“Nevertheless divers of Asher and Manasseh and of Zebulun humbled themselves, and came to Jerusalem.”
“So there was great joy in Jerusalem: for since the time of Solomon the son of David king of Israel there was not the like in Jerusalem.”
“Rejoice in the Lord alway: and again I say, Rejoice.”