A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
2 Chronicles 11:1
ch2 11:1REHOBOAM, RAISING AN ARMY TO SUBDUE ISRAEL, IS FORBIDDEN BY SHEMAIAH. (2Ch. 11:1-17)
Rehoboam . . . gathered of the house of Judah and Benjamin . . . to fight against Israel--(See Kg1 12:21-24).
2 Chronicles 11:5
ch2 11:5built cities for defence in Judah--This is evidently used as the name of the southern kingdom. Rehoboam, having now a bitter enemy in Israel, deemed it prudent to lose no time in fortifying several cities that lay along the frontier of his kingdom. Jeroboam, on his side, took a similar precaution (Kg1 12:25). Of the fifteen cities named, Aijalon, now Yalo, and Zorah, now Surah, between Jerusalem and Jabneh [ROBINSON], lay within the province of Benjamin. Gath, though a Philistine city, had been subject to Solomon. And Etham, which was on the border of Simeon, now incorporated with the kingdom of Israel, was fortified to repel danger from that quarter. These fortresses Rehoboam placed under able commanders and stocked them with provisions and military stores, sufficient, if necessary, to stand a siege. In the crippled state of his kingdom, he seems to have been afraid lest it might be made the prey of some powerful neighbors.
2 Chronicles 11:13
ch2 11:13the priests and the Levites . . . resorted to him out of all their coasts--This was an accession of moral power, for the maintenance of the true religion is the best support and safeguard of any nation; and as it was peculiarly the grand source of the strength and prosperity of the Hebrew monarchy, the great numbers of good and pious people who sought an asylum within the territories of Judah contributed greatly to consolidate the throne of Rehoboam. The cause of so extensive an emigration from the kingdom of Israel was the deep and daring policy of Jeroboam, who set himself to break the national unity by entirely abolishing, within his dominions, the religious institutions of Judaism. He dreaded an eventual reunion of the tribes if the people continued to repair thrice a year to worship in Jerusalem as they were obliged by law to do. Accordingly, on pretense that the distance of that city was too great for multitudes of his subjects, he fixed upon two more convenient places, where he established a new mode of worshipping God under gross and prohibited symbols [Kg1 12:26-33]. The priests and Levites, refusing to take part in the idolatrous ceremonies, were ejected from their living [Ch2 11:13-14]. Along with them a large body of the people who faithfully adhered to the instituted worship of God, offended and shocked by the impious innovations, departed from the kingdom.
2 Chronicles 11:15
ch2 11:15he ordained him priests--The persons he appointed to the priesthood were low and worthless creatures (Kg1 12:31; Kg1 13:33); any were consecrated who brought a bullock and seven rams (Ch2 13:9; Exo 29:37).
for the high places--Those favorite places of religious worship were encouraged throughout the country.
for the devils--a term sometimes used for idols in general (Lev 17:7). But here it is applied distinctively to the goat deities, which were probably worshipped chiefly in the northern parts of his kingdom, where the heathen Canaanites still abounded.
for the calves which he had made--figures of the ox gods Apis and Mnevis, with which Jeroboam's residence in Egypt had familiarized him. (See on Kg1 12:26).
2 Chronicles 11:17
ch2 11:17they strengthened the kingdom of Judah--The innovating measures of Jeroboam were not introduced all at once. But as they were developed, the secession of the most excellent of his subjects began, and continuing to increase for three years, lowered the tone of religion in his kingdom, while it proportionally quickened its life and extended its influence in that of Judah.
2 Chronicles 11:18
ch2 11:18HIS WIVES AND CHILDREN. (Ch2 11:18-23)
Rehoboam took Mahalath--The names of her father and mother are given. Jerimoth, the father, must have been the son of one of David's concubines (Ch1 3:9). Abihail was, of course, his cousin, previous to their marriage.
2 Chronicles 11:20
ch2 11:20after her he took Maachah . . . daughter--that is, granddaughter (Sa2 14:27) of Absalom, Tamar being, according to JOSEPHUS, her mother. (Compare Sa2 18:18).
2 Chronicles 11:21
ch2 11:21he took eighteen wives, and threescore concubines--This royal harem, though far smaller than his father's, was equally in violation of the law, which forbade a king to "multiply wives unto himself" [Deu 17:17].
2 Chronicles 11:22
ch2 11:22made Abijah . . . chief . . . ruler among his brethren--This preference seems to have been given to Abijah solely from the king's doting fondness for his mother and through her influence over him. It is plainly implied that Abijah was not the oldest of the family. In destining a younger son for the kingdom, without a divine warrant, as in Solomon's case, Rehoboam acted in violation of the law (Deu 21:15).
2 Chronicles 11:23
ch2 11:23he dealt wisely--that is, with deep and calculating policy (Exo 1:10).
and dispersed of all his children . . . unto every fenced city--The circumstance of twenty-eight sons of the king being made governors of fortresses would, in our quarter of the world, produce jealousy and dissatisfaction. But Eastern monarchs ensure peace and tranquillity to their kingdom by bestowing government offices on their sons and grandsons. They obtain an independent provision, and being kept apart, are not likely to cabal in their father's lifetime. Rehoboam acted thus, and his sagacity will appear still greater if the wives he desired for them belonged to the cities where each son was located. These connections would bind them more closely to their respective places. In the modern countries of the East, particularly Persia and Turkey, younger princes were, till very lately, shut up in the harem during their father's lifetime; and, to prevent competition, they were blinded or killed when their brother ascended the throne. In the former country the old practice of dispersing them through the country as Rehoboam did, has been again revived.