1 Chronicles 27:1

Now the children of Israel after their number,.... Not the whole body of the people, but the militia of the nation; for after the account of the division of the priests and Levites into courses, follows an account of the militia of the nation, being divided also into monthly courses; which, though done in the beginning of David's reign, as Kimchi and Jarchi observe, yet is here related; and that it was so soon is clear from the instance of Asahel, who was killed while David was king in Hebron, 1 Chronicles 27:7 to wit,

the chief fathers; the chief men in the tribes, the princes of them, not the natural fathers of the soldiers in each course, as a learned man suggests i: since it can never be thought that such a number sprung from those as made a course of 24,000; for they are distinct from the captains and officers after mentioned, under which the soldiers were; besides, why should they be called "chief fathers?" these, no doubt, were the general officers or princes, under which the captains and inferior officers were:

and captains of thousands and hundreds; in the several tribes:

and their officers; that were under them:

that served the king in any matter of the courses, which came in and went out month by month, throughout all the months of the year; by which it appears that the militia of the kingdom was divided into twelve courses, which served each month by turns; when one went out another came in; by which means the king was well supported and guarded, and had an army at once at command upon any insurrection or war that might arise; and each course serving but one month in a year, it was no great burden upon them, even if they maintained themselves, since they were at leisure, the other eleven months, to attend to their business; and especially if it was, as Jarchi observes, that not the poor but the rich were selected for this service:

of every course were twenty and four thousand; so that the twelve courses amounted to 288,000 men.

i Delaney's Life of King David, vol. 1. p. 319.