1 Chronicles 23:5

³  Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand.

⁴  Of which, twenty and four thousand were to set forward the work of the house of the LORD; and six thousand were officers and judges:

⁵  Moreover four thousand were porters; and four thousand praised the LORD with the instruments which I made, said David, to praise therewith.

⁶  And David divided them into courses among the sons of Levi, namely, Gershon, Kohath, and Merari.

⁷  Of the Gershonites were, Laadan, and Shimei.