1. There was the military department, at the head of which was Joab, or rather he was over "the host"--the great muster of the people for military purposes. A more select body, "the Cherethites and the Pelethites," seems to have formed a bodyguard for the king, or a band of household troops, and was under a separate commander. The troops forming "the host" were divided into twelve courses of twenty-four thousand each, regularly officered, and for one month of the year the officers of one of the courses, and probably the people, or some of them, attended on the king at Jerusalem (1 Chron. xxvii. 1). Of the most distinguished of his soldiers who excelled in feats of personal valour, David seems to have formed a legion of honour, conspicuous among whom were the thirty honourable, and the three who excelled in honour (2 Sam. xxiii. 28). It is certain that whatever extra power could be given by careful organization to the fighting force of the country, the army of Israel under David possessed it in the fullest degree.
2. There was the civil department, at the head of which were Jehoshaphat the recorder and Seraiah the scribe or secretary. While these were in attendance on David at Jerusalem, they did not supersede the ordinary home rule of the tribes of Israel. Each tribe had still its prince or ruler, and continued, under a general superintendence from the king, to conduct its local affairs (1 Chron. xxvii. 16-22). The supreme council of the nation continued to assemble on occasions of great national importance (1 Chron. xxviii. 1), and though its influence could not have been so great as it was before the institution of royalty, it continued an integral element of the constitution, and in the time of Rehoboam, through its influence and organization (1 Kings xii. 3, 16), the kingdom of the ten tribes was set up, almost without a struggle (1 Chron. xxiii. 4). This home-rule system, besides interesting the people greatly in the prosperity of the country, was a great check against the abuse of the royal authority; and it is a proof that the confidence of Rehoboam in the stability of his government, confirmed perhaps by a superstitious view of that promise to David, must have been an absolute infatuation, the product of utter inexperience on his part, and of the most foolish counsel ever tendered by professional advisers.
3. Ecclesiastical administration. The capture of Jerusalem and its erection into the capital of the kingdom made a great change in ecclesiastical arrangements. For some time before it would have been hard to tell where the ecclesiastical capital was to be found. Shiloh had been stripped of its glory when Ichabod received his name, and the Philistine armies destroyed the place. Nob had shared a similar fate at the hands of Saul. The old tabernacle erected by Moses in the wilderness was at Gibeon (1 Chron. xxi. 29), and remained there even after the removal of the ark to Zion (1 Kings iii. 4). At Hebron, too, there must have been a shrine while David reigned there. But from the time when David brought up the ark to Jerusalem, that city became the greatest centre of the national worship. There the services enjoined by the law of Moses were celebrated; it became the scene of the great festivals of Passover, Pentecost, and Tabernacles.
We are told that the heads of the ecclesiastical department were Zadok the son of Ahitub and Ahimelech the son of Abiathar. These represented the elder and the younger branches of the priesthood. Zadok was the lineal descendant of Eleazar, Aaron's son (1 Chron. vi. 12), and was therefore the constitutional successor to the high-priesthood. Ahimelech the son of Abiathar represented the family of Eli, who seems to have been raised to the high-priesthood out of order, perhaps in consequence of the illness or incompetence of the legitimate high-priest. It is of some interest to note the fact that under David two men were at the head of the priesthood, much as it was in the days of our Lord, when Annas and Caiaphas are each called the high-priest. The ordinary priests were divided into four-and-twenty courses, and each course served in its turn for a limited period, an arrangement which still prevailed in the days of Zacharias, the father of John the Baptist. A systematic arrangement of the Levites was likewise made; some were allocated to the service of the Temple, some were porters, some were singers, and some were officers and judges. Of the six thousand who filled the last-named office, "chief fathers" as they were called, nearly a half were allocated among the tribes east of the Jordan, as being far from the centre, and more in need of oversight. It is probable that this large body of Levites were not limited to strictly judicial duties, but that they performed important functions in other respects, perhaps as teachers, physicians, and registrars. It is not said that Samuel's schools of the prophets received any special attention, but the deep interest that David must have taken in Samuel's work, and his early acquaintance with its effects, leave little room to doubt that these institutions were carefully fostered, and owed to David some share of the vitality which they continued to exhibit in the days of Elijah and Elisha. It is very probable that the prophets Gad and Nathan were connected with these institutions.