The Levites: David by his Last Words had Them Numbered from Twenty Years Old
Source: TTT
1 Chronicles 23:24, 27
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. / For according to the final instructions of David, the Levites twenty years of age or older were counted,