Jamieson, Fausset and Brown on Ezra 2:36-39

36-39. The priests--Each of their families was ranged under its prince or head, like those of the other tribes. It will be remembered that the whole body was divided into twenty-four courses, one of which, in rotation, discharged the sacerdotal duties every week, and each division was called after the name of its first prince or chief. It appears from this passage that only four of the courses of the priests returned from the Babylonish captivity; but these four courses were afterwards, as the families increased, divided into twenty-four, which were distinguished by the names of the original courses appointed by David [1Ch 23:6-13]. Hence we find the course of Abijah or Abia (1Ch 24:10) subsisting at the commencement of the Christian era (Lu 1:5).