And there were more chief men found of the sons of Eleazar than of the sons of Ithamar,.... Or heads of men, heads of their fathers' houses and families:and thus were they divided; among the sons of Eleazar there were sixteen chief men of the house of their fathers, and eight among the sons of Ithamar, according to the house of their fathers; in all twenty four, and into so many classes or courses did David divide them; Jarchi says at first when the tabernacle was at Shiloh, there were but sixteen courses, eight from Eleazar, and eight from Ithamar, as is explained in the treatise of fasting ; but when David saw that there were more heads of men, or chief men of Eleazar's, he divided the courses of Eleazar into two parts, and fixed sixteen courses; and the courses of Ithamar he established as at first, eight courses; left them as they were, which he thinks appears from 1Ch 24:6 but of the former number of courses, and when and by whom fixed, the Jews are divided ;See Gill on "Lu 1:5".
Perhaps there were none before David's time. T. Bab. Taanith, fol. 27. 1. T. Bab. Taanith, fol. 27.