Bible Verses About The Levites: Divided them into four classed

Of these, twenty and four thousand were to oversee the work of the house of Jehovah; and six thousand were officers and judges;

and four thousand were doorkeepers; and four thousand praised Jehovah with the instruments which I made, said David, to praise therewith.

And David divided them into courses according to the sons of Levi: Gershon, Kohath, and Merari.