The most important thing about the translation of this verse is to make it quite clear to readers that there has been a definite shift in speakers. The boast of King Sennacherib concludes at the end of verse 24. Here the prophet answers him in the name of Yahweh. Moffatt adds the words “so asks the Eternal” for the sake of clarity. This may be a good idea in other languages although it will be less necessary if the direct quotation of Sennacherib in verses 23b-24 has been transformed to indirect speech as recommended.
Have you not heard that I determined it long ago?: This question is rhetorical. God is amazed that Sennacherib does not know what God is about to say. If translators decide to make this rhetorical question a statement, NET Bible provides a good model with “Certainly you must have heard! Long ago I worked it out.”
A literal rendering of the clause I determined it long ago will almost certainly make readers ask what the LORD determined long ago. The answer, which should be made clear in translation, is the expansion of the kingdom of Assyria that Sennacherib has been talking about in verses 23b-24. By stating that the activities of the Assyrians were a part of God’s overall plan, the prophet asserts that Sennacherib was little more than Yahweh’s instrument and therefore had no reason to boast. Contemporary English Version translates “I planned all this long ago.” But if this does not clarify the meaning, translators may consider something like “I planned the expansion of your kingdom long ago.”
I planned from days of old: The verb planned is parallel to determined, and from days of old has the same meaning as long ago in the previous line. The repetition is intentional and serves to emphasize the truth of God’s predetermined plan of which the Assyrian king was but a small part and for which he could not legitimately take credit.
What now I bring to pass: The verb bring to pass is literally “cause to come.” The verb form in this verse may pose a problem for some translators. Revised English Bible is probably correct in giving it a past tense meaning, saying “now I have brought it about” (similarly New American Bible). Since Sennacherib had already brought about the destruction described, the present tense rendering of Revised Standard Version is confusing.
You should turn fortified cities into heaps of ruins: This action on the part of the Assyrian king is described in 2 Kgs 18.13.
Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Kings, Volume 2. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here .