Now the children of Israel after their number, to wit, the chief fathers and captains of thousands and hundreds, and their officers 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, of every course were twenty and four thousand.
Captains of thousands and hundreds. The division of the people was the same for military as for civil purposes (cf. Exodus 18:21 with Numbers 31:14); at least, the rotation of 24,000 men appointed to attend David every month is described so as to indicate their being arranged by this old and familiar division (see Graves,
ii., p. 15; Lowman, 'On the Government of the Hebrews,' p. 73). The legions of 24,000 were divided into regiments of 1,000, and these again into companies of 100 men, under the direction of their respective subalterns, there being, of course, twenty-four captains of thousands and 240 centurions.
And their officers - the Shoterim, who, in the army, performed the duty of the commissariat, keeping the muster-roll, etc.
Came in and went out month by month. Here is an account of the standing military force of Israel. A militia, formed, it would seem, at the beginning of David's reign (see the note at 1 Chronicles 27:7), was raised in the following order: Twelve legions, corresponding to the number of tribes, were enlisted in the king's service. Each legion comprised a body of 24,000 men, whose term of service was a month in rotation, and who were stationed either at Jerusalem or in any other place where they might be required. There was thus always a force sufficient for the ordinary purposes of state, as well as for resisting sudden attacks or popular tumults; and when extraordinary emergencies demanded a larger force, the whole standing army could easily be called to arms, amounting to 288,000, or to 300,000, including the 12,000 officers that naturally attended on the twelve princes (1 Chronicles 27:16-24). Such a military establishment would be burdensome neither to the country nor to the royal exchequer; because the expense of maintenance would be borne probably by the militia-man himself, or furnished out of the common fund of his tribe. On the expiration of the term, every soldier returned to the pursuits and duties of private life during the other eleven months of the year. Whether the same individuals were always enrolled cannot be determined. The probability is, that provided the requisite number was furnished, no stricter scrutiny would be made. The rotation system being established, each division knew its own month, as well as the name of the commander under whom it was to serve. These commanders are called the chief fathers' - i:e., the hereditary heads of tribes, who, like chieftains of clans, possessed great power and influence.