Who was Zimri?
Zimri was the 5th king of Israel, but who occupied the throne only seven days ( 1 Kings 16:9-20 ).
Zimri had been captain of half the chariots under Elah, and, as it seems, made use of his position to conspire against his master. The occasion for his crime was furnished by the absence of the army, which, under the direction of Omri, was engaged in the siege of the Philistine town Gibbethon.
While Elah was in a drunken debauch in the house of his steward Arza, who may have been an accomplice in the plot, he was foully murdered by Zimri, who ascended the throne and put the remnant of Elah's family to death, thus fulfilling the prophecy of Jehu concerning the house of Baasha.
However, the conspiracy lacked the support of the people, for word of the crime no sooner reached Gibbethon, than the army raised Omri to the throne of Israel. Omri at once hastened to Tirzah and captured the place, which as it seems offered little resistance. Zimri resolved to die as king, and accordingly set fire to the palace with his own hands, and perished in the flames that he had kindled.
Thus came to an ignominious end the short reign which remained as a blot even upon the blood-stained record of the deeds of violence that ushered in the change of dynasties in the Northern Kingdom, for the foul crime was abhorred even among arch plotters. When Jehu entered Jezreel he was met with Jezebel's bitter taunt, "Is it peace, thou Zimri, thy master's murderer?" (2 Kings 9:31 ). The historian too, in the closing formula of the reign, specially mentions "his treason that he worked."
IBSE, "Isaac" (in the public domain) with minor edits.