1 Chronicles 27:1 - Joseph Benson’s Commentary on the Old and New Testaments

Now the children of Israel, &c. After the settlement of sacred affairs, we have here an account of the manner in which the army, or militia, as we may call it, was disposed. It was distributed into twelve legions, each consisting of twenty-four thousand men, who were commanded by one of the chief of the fathers; under whom there were captains of thousands, such as we now call colonels; and then under them captains of hundreds. Each of these legions attended one month, for the security of the king and kingdom; at the end of which they were dismissed, and another legion, with their general, succeeded: so that their course came but once in a year, and that only for one month, which was no considerable burden to them. That served the king in any matter of the courses In all the business in which the king had occasion for these persons. Which came in and went out, &c. Who, being armed and mustered, were to wait upon the king, at Jerusalem, or other places, as the king should see fit. By this order near three hundred thousand of his people were instructed and exercised in the use of their arms, and fitted for the defence of their king and kingdom when it should be needful, and in the mean time sufficient provision was made against any sudden tumults or irruptions of enemies. And this monthly course was contrived that the burden of it might be easy, and equally distributed among the people.