Albert Barnes Commentary Ezra 3:8

"Now in the second year of their coming unto the house of God at Jerusalem, in the second month, began Zerubbabel the son of Shealtiel, and Jeshua the son of Jozadak, and the rest of their brethren the priests and the Levites, and all they that were come out of the captivity unto Jerusalem, and appointed the Levites, from twenty years old and upward, to have the oversight of the work of the house of Jehovah." — Ezra 3:8 (ASV)

To the house of God - that is, to the place where the house of God had been, and where God was believed still to have His special dwelling.

And appointed the Levites - This is the emphatic clause of the present verse. Though so small a number of Levites had returned from Babylon (Ezra 2:40), yet they were especially singled out to be entrusted with the task of superintending and advancing the building of the temple.