Charles Ellicott 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)

In the second year. —The second year of Cyrus, B.C. 537, was their second year in the holy place.

In the second month. —Zif, chosen apparently because it was the same month in which Solomon laid the first foundation (1 Kings 6:1).

Appointed the Levites, from twenty years. —Their appointment to superintend, and their specified age, are in strict harmony with the original ordinances of David (1 Chronicles 23:24).