2 Chronicles 21:4 - Joseph Benson’s Commentary on the Old and New Testaments

He strengthened himself Hardened his heart, as the word חזק , chazak, often signifies; and slew all his brethren with the sword Either by false accusation, under colour of law, or rather by assassination, pretending, it is likely, that he could not think himself safe in the government till they were taken out of the way. Those that mean ill themselves, are commonly, without cause, jealous of those about them. And divers also of the princes of Israel Either, 1st, Of Judah, here called Israel, as in 2 Chronicles 21:2. Or rather, 2d, Of Israel properly so called; not the princes of all Israel, or of the several tribes thereof, but the chief of those Israelites who, out of love to God and the true religion, had forsaken their estates in the kingdom of Israel, and were now incorporated with the kingdom of Judah: these he slew, because he thought they would be most zealous for that religion which he was resolved to oppose.