מלכים ב יח:כה פירוש: רש״י

Is it with other than Adonoy. Did I come without permission? Yeshayohu already prophesied in the days of Achaz your father, ”Adonoy shall bring upon you and upon your people, etc., the king of Ashur.”¹⁷Yeshayohu 7:17. Radak cites another verse from Yeshayohu's prophecy, “and therefore the LRD is bringing upon them the mighty and abundant waters of the river, the king of Ashur, etc.,” in Yeshayohu 8:7. Sancheiriv therefore believed that he was acting with Divine approval.

And to destroy it. This he added of his own accord.