This verse describes the bloody aftermath of Jehu's cunning plan to eliminate the worshipers of Baal in Israel. Here's a breakdown:

"As soon as he had finished offering the burnt offering...": Jehu, under the guise of zealous Baal worship, had gathered all the Baal worshipers into the temple. The offering was likely part of this deception, meant to lull the worshipers into a false sense of security.

"...Jehu said to the guard and to the captains, 'Go in and kill them! Let no one escape.'...": This is the turning point. Jehu reveals his true intentions. He orders his soldiers (the guard and captains) to massacre everyone inside the temple. The command "Let no one escape" emphasizes the ruthlessness and totality of the intended extermination.

"...So they struck them with the edge of the sword.": This is a graphic description of the slaughter. The "edge of the sword" signifies a swift and brutal death.

"The guard and the captains threw the bodies out, and went to the inner shrine of the house of Baal.": After the massacre, the soldiers removed the corpses from the temple, desecrating them further. The fact that they then proceeded to the "inner shrine of the house of Baal" suggests they were continuing to destroy and desecrate anything associated with Baal worship.

In essence, this verse signifies a brutal act of religious cleansing orchestrated by Jehu. It demonstrates his extreme commitment to eradicating Baal worship from Israel, even if it meant resorting to treachery and mass murder.

Context is Important:

It's crucial to understand this verse within the broader context of the books of Kings and the religious history of Israel.

Religious Conflict: The conflict between Yahweh worship and Baal worship was a central theme in the Old Testament. Kings often swayed between promoting one or the other.
Jehu's Motivation: Jehu was anointed king by a prophet of Yahweh (God of Israel) and tasked with destroying the house of Ahab, who had promoted Baal worship. He saw the elimination of Baal worship as crucial to restoring Israel's covenant with God.
Ethical Considerations: Modern readers often struggle with the violence depicted in the Old Testament, particularly when it's seemingly sanctioned by divine authority. It raises complex questions about morality, religious zeal, and the interpretation of scripture.
Historical Perspective: It's important to consider the historical context and the standards of warfare and religious practice in the ancient Near East. While the events are undeniably violent, they were likely perceived differently in their time.

In summary, this verse is a pivotal moment in the narrative, revealing the shocking extent of Jehu's purge and highlighting the religious and political struggles of ancient Israel. It is a controversial passage that requires careful consideration and contextual understanding.