Ezra 6:18
“And they set the priests in their divisions, and the Levites in their courses, for the service of God, which is at Jerusalem; as it is written in the book of Moses.”
And the children of Israel, the priests, and the Levites, and the rest of the children of the captivity, kept the dedication of this house of God with joy,
And offered at the dedication of this house of God an hundred bullocks, two hundred rams, four hundred lambs; and for a sin offering for all Israel, twelve he goats, according to the number of the tribes of Israel.
And they set the priests in their divisions, and the Levites in their courses, for the service of God, which is at Jerusalem; as it is written in the book of Moses.
And the children of the captivity kept the passover upon the fourteenth day of the first month.
For the priests and the Levites were purified together, all of them were pure, and killed the passover for all the children of the captivity, and for their brethren the priests, and for themselves.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“Bring the tribe of Levi near, and present them before Aaron the priest, that they may minister unto him.”
“And they ministered before the dwelling place of the tabernacle of the congregation with singing, until Solomon had built the house of the Lord in Jerusalem: and then they waited on their office according to their order.”
“And David divided them into courses among the sons of Levi, namely, Gershon, Kohath, and Merari.”
“And he appointed, according to the order of David his father, the courses of the priests to their service, and the Levites to their charges, to praise and minister before the priests, as the duty of every day required: the porters also by their courses at every gate: for so had David the man of God commanded.”
“And Hezekiah appointed the courses of the priests and the Levites after their courses, every man according to his service, the priests and Levites for burnt offerings and for peace offerings, to minister, and to give thanks, and to praise in the gates of the tents of the Lord.”