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
4 Kings (2 Kings) 10:1
kg2 10:1JEHU CAUSES SEVENTY OF AHAB'S CHILDREN TO BE BEHEADED. (2Ki. 10:1-17)
Ahab had seventy sons in Samaria--As it appears (Kg2 10:13), that grandsons are included it is probable that this number comprehended the whole posterity of Ahab. Their being all assembled in that capital might arise from their being left there on the king's departure for Ramoth-gilead, or from their taking refuge in some of the strongholds of that city on the news of Jehu's conspiracy. It may be inferred from the tenor of Jehu's letters that their first intention was to select the fittest of the royal family and set him up as king. Perhaps this challenge of Jehu was designed as a stroke of policy on his part to elicit their views, and to find out whether they were inclined to be pacific or hostile. The bold character of the man, and the rapid success of his conspiracy, terrified the civic authorities of Samaria and Jezreel into submission.
4 Kings (2 Kings) 10:5
kg2 10:5he that was over the house--the governor or chamberlain of the palace.
the bringers-up of the children--Anciently, and still also in many Eastern countries, the principal grandees were charged with the support and education of the royal princes. This involved a heavy expense which they were forced to bear, but for which they endeavored to find some compensation in the advantages of their connection with the court.
4 Kings (2 Kings) 10:6
kg2 10:6take ye the heads of the men, your master's sons--The barbarous practice of a successful usurper slaughtering all who may have claims to the throne, has been frequently exemplified in the ancient and modern histories of the East.
4 Kings (2 Kings) 10:8
kg2 10:8Lay ye them in two heaps at the entering in of the gate, &c.--The exhibition of the heads of enemies is always considered a glorious trophy. Sometimes a pile of heads is erected at the gate of the palace; and a head of peculiarly striking appearance selected to grace the summit of the pyramid.
4 Kings (2 Kings) 10:9
kg2 10:9said to all the people, Ye be righteous, &c.--A great concourse was assembled to gaze on this novel and ghastly spectacle. The speech which Jehu addressed to the spectators was artfully framed to impress their minds with the idea that so wholesale a massacre was the result of the divine judgments denounced on the house of Ahab; and the effect of it was to prepare the public mind for hearing, without horror, of a similar revolting tragedy which was soon after perpetrated, namely, the extinction of all the influential friends and supporters of the dynasty of Ahab, including those of the royal house of Judah.
4 Kings (2 Kings) 10:13
kg2 10:13We are the brethren of Ahaziah--that is, not full, but step-brothers, sons of Jehoram by various concubines. Ignorant of the revolution that had taken place, they were travelling to Samaria on a visit to their royal relatives of Israel, when they were seized and put to death, because of the apprehension that they might probably stimulate and strengthen the party that still remained faithful in their allegiance to Ahab's dynasty.
children of the queen--that is, of the queen mother, or regent, Jezebel.
4 Kings (2 Kings) 10:15
kg2 10:15Jehonadab the son of Rechab--(See Ch1 2:55). A person who, from his piety and simple primitive manner of life (Jer. 35:1-19), was highly esteemed, and possessed great influence in the country. Jehu saw in a moment the advantage that his cause would gain from the friendship and countenance of this venerable man in the eyes of the people, and accordingly paid him the distinguished attention of inviting him to a seat in his chariot.
give me thine hand--not simply to aid him in getting up, but for a far more significant and important purpose--the giving, or rather joining hands, being the recognized mode of striking a league or covenant, as well as of testifying fealty to a new sovereign; accordingly, it is said, "he [Jehonadab] gave him [Jehu] his hand."
4 Kings (2 Kings) 10:19
kg2 10:19HE DESTROYS THE WORSHIPPERS OF BAAL. (Kg2 10:18-29)
call unto me all the prophets of Baal--The votaries of Baal are here classified under the several titles of prophets, priests, and servants, or worshippers generally. They might be easily convened into one spacious temple, as their number had been greatly diminished both by the influential ministrations of Elijah and Elisha, and also from the late King Joram's neglect and discontinuance of the worship. Jehu's appointment of a solemn sacrifice in honor of Baal, and a summons to all his worshippers to join in its celebration, was a deep-laid plot, which he had resolved upon for their extinction, a measure in perfect harmony with the Mosaic law, and worthy of a constitutional king of Israel. It was done, however, not from religious, but purely political motives, because he believed that the existence and interests of the Baalites were inseparably bound up with the dynasty of Ahab and because he hoped that by their extermination he would secure the attachment of the far larger and more influential party who worshipped God in Israel. Jehonadab's concurrence must have been given in the belief of his being actuated solely by the highest principles of piety and zeal.
4 Kings (2 Kings) 10:22
kg2 10:22Bring forth vestments for all the worshippers of Baal--The priests of Baal were clad, probably, in robes of white byssus while they were engaged in the functions of their office, and these were kept under the care of an officer in a particular wardrobe of Baal's temple. This treacherous massacre, and the means taken to accomplish it, are paralleled by the slaughter of the Janissaries and other terrible tragedies in the modern history of the East.
4 Kings (2 Kings) 10:29
kg2 10:29Howbeit from the sins of Jeroboam . . . Jehu departed not from after them--Jehu had no intention of carrying his zeal for the Lord beyond a certain point, and as he considered it impolitic to encourage his subjects to travel to Jerusalem, he re-established the symbolic worship of the calves.