8 In the second month of the second year after they had arrived at the house of God in Jerusalem, Zerubbabel son of Shealtiel, Jeshua son of Jozadak, and the rest of their associates including the priests, the Levites, and all who had returned to Jerusalem from the captivity, began the work. They appointed Levites twenty years of age or older to supervise the construction of the house of the LORD.
Ezra 3:8 Cross References - BSB
Numbers 4:3
3 men from thirty to fifty years old—everyone who is qualified to serve in the work at the Tent of Meeting.
1 Chronicles 23:4
4 “Of these,” said David, “24,000 are to oversee the work of the house of the LORD, 6,000 are to be officers and judges,
1 Chronicles 23:24-32
24 These were the descendants of Levi by their families—the heads of families, registered individually by name—those twenty years of age or older who worked in the service of the house of the LORD.
25 For David had said, “The LORD, the God of Israel, has given rest to His people and has come to dwell in Jerusalem forever.
26 So now the Levites no longer need to carry the tabernacle or any of the articles for its service.”
27 For according to the final instructions of David, the Levites twenty years of age or older were counted,
28 but their duty was to assist the descendants of Aaron with the service of the house of the LORD, being responsible for the courts and chambers, the purification of all the holy things, and the work of the service of the house of God,
29 as well as for the rows of the showbread, the fine flour for the grain offering, the wafers of unleavened bread, the baking, the mixing, and all measurements of quantity and size.
30 They were also to stand every morning to give thanks and praise to the LORD, and likewise in the evening.
31 Whenever burnt offerings were presented to the LORD on the Sabbaths, New Moons, and appointed feasts, they were to serve regularly before the LORD in the numbers prescribed for them.
32 So the Levites were to carry out the responsibilities for the Tent of Meeting and the Holy Place, and, under their brothers the descendants of Aaron, the service of the house of the LORD.
Ezra 4:3
3 But Zerubbabel, Jeshua, and the other heads of the families of Israel replied, “You have no part with us in building a house for our God, since we alone must build it for the LORD, the God of Israel, as Cyrus king of Persia has commanded us.”