Ezra 3:8
And in the second year of their coming to the house of God at Jerusalem, in the second month, began Zerubbabel the son of Shealtiel, and Jeshua the son of Jozadak, and the remnant of their brethren the priests and the Levites, and all they that had come out of the captivity to Jerusalem; and they appointed the Levites, from twenty years old and upward, to superintend the work of the house of Jehovah.
Numbers 4:3
from thirty years old and upward even unto fifty years old, all that enter into the service, to do the work in the tent of meeting.
1 Chronicles 23:4
Of these, twenty-four thousand were to preside over the work of the house of Jehovah; and six thousand were officers and judges;
1 Chronicles 23:24-32
These were the sons of Levi according to their fathers' houses, the chief fathers, as they were reckoned, by number of names by their polls, who did the work of the service of the house of Jehovah, from twenty years old and upward.
Ezra 4:3
But Zerubbabel and Jeshua and the rest of the chief fathers of Israel said to them, Ye have nothing to do with us to build a house to our God, but we alone will build to Jehovah the God of Israel, as king Cyrus, the king of Persia, has commanded us.