Albert Barnes Commentary 2 Kings 6:31

"Then he said, God do so to me, and more also, if the head of Elisha the son of Shaphat shall stand on him this day." — 2 Kings 6:31 (ASV)

God do so ... - Jehoram uses almost the very words of his wicked mother when she sought the life of Elijah.

The head of Elisha - Beheading was not an ordinary Jewish punishment. The Law did not sanction it. But in Assyria, Babylonia, and generally throughout the East, it was the most common form of capital punishment. It is not quite clear why Elisha was to be punished. Perhaps Jehoram reasoned from his other miracles that he could provide deliverance from the present peril, if he chose to.