Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
An account of the twelve captains who were over the monthly course of twenty-four thousand men; each captain serving one month in turn, Ch1 27:1. The names of the twelve, and the months in which they served, Ch1 27:2-15. The names of the rulers of the twelve tribes, Ch1 27:16-22. The reasons why the whole number of Israel and Judah had not been taken, Ch1 27:23, Ch1 27:24. The persons who were over the king's property, treasures, fields, flocks, etc., Ch1 27:25-31. His officers of state, Ch1 27:32-34.
The chief fathers and captains of thousands - The patriarchs, chief generals, or generals of brigade. This enumeration is widely different from the preceding. In that, we have the orders and courses of the priests and the Levites in their ecclesiastical ministrations; in this, we have the account of the order of the civil service, that which related simply to the political state of the king and the kingdom. Twenty-four persons, chosen out of David's worthies, each of whom had a second, were placed over twenty-four thousand men, who all served a month in turn at a time; and this was the whole of their service during the year, after which they attended to their own affairs. Thus the king had always on foot a regular force of twenty-four thousand, who served without expense to him or the state, and were not oppressed by the service, which took up only a twelfth part of their time, and by this plan he could at any time, when the exigency of the state required it, bring into the field twelve times twenty-four thousand, or two hundred and eighty-eight thousand fighting men, independently of the twelve thousand officers, which made in the whole an effective force of three hundred thousand soldiers; and all these men were prepared, disciplined, and ready at a call, without the smallest expense to the state or the king. These were, properly speaking, the militia of the Israelitish kingdom. See Calmet.
First course for the first month - Instead of mentioning first, second, third, etc., month, the Targum names them thus: First month, Nisan; second, Aiyar; third, Sivan; fourth, Tammuz; fifth, Ab; sixth, Elul; seventh, Tishri; eighth, Marchesvan; ninth, Cisleu; tenth, Tebeth; eleventh, Shebat; twelfth, Adar. No mention is made of a veadar or intercalary month.
Benaiah the son of Jehoiada, a chief priest - Why should not this clause be read as it is in the Hebrew? "Benaiah, the son of Jehoiada the priest, a captain; and in his course," etc. Or, as the Targum has it, "The third captain of the host for the month Sivan was Benaiah, the son of Jehoiada the priest, who was constituted a chief." He is distinguished from Benaiah, the Pirathonite, who was over the eleventh month. Some think that the original word הכהן haccohen, which generally signifies priest, should be translated here a principal officer; so the margin has it. But, in the Old Testament, כהן cohen signifies both prince and priest; and translating it by the former removes the difficulty from this place, for we well know that Benaiah never was a priest.
Asahel the brother of Joab - This verse proves that the division and arrangement mentioned above were made before David was acknowledged king in Hebron; for Asahel, the brother of Joab, who was fourth captain, was slain by Abner, while Ishbosheth reigned over Israel at Mahanaim, Sa2 2:19-23.
Over the tribes of Israel - In this enumeration there is no mention of the tribes of Asher and Gad. Probably the account of these has been lost from this register. These rulers appear to have been all honorary men, without pay, like the lords lieutenants of our counties.
Neither was the number put in the account - Joab did not return the whole number; probably the plague began before he had finished: or, he did not choose to give it in, as he had entered on this work with extreme reluctance; and he did not choose to tell the king how numerous they were.
Over the king's treasures - We see from these verses in what the personal property of David consisted: -
1. Treasures, gold, silver, etc.
2. Goods and grain in castles, cities villages, and in the fields.
3. Vineyards and their produce.
4. Olive-trees and their produce.
5. Neat cattle, in different districts.
6. Camels and asses: they had no horses.
7. Flocks, sheep, goats, etc.
And after Ahithophel - The Targum is curious: "When they went to war, they asked counsel of Ahithophel; and, after the counsel of Ahithophel, they inquired by Urim and Thummim of Jehoiada, the son of Benaiah, prince of the Sanhedrin, and chief of the priesthood; and from Abiathar, the high priest. And after they had inquired by Urim and Thummim, they went out to battle, well armed with bows and slings; and Joab, the general of the king's troops, led them on." It is worthy of remark, that Obil, an Ishmaelite or Arab, was put over the camels, which is a creature of Arabia; and that Jaziz, a Hagarene, (the Hagarenes were shepherds by profession), was put over the flocks: nothing went by favor; each was appointed to the office for which he was best qualified; and thus men of worth were encouraged, and the public service effectually promoted.