Translators should compare verses 23-29 to 10.5-19. In both passages Assyria is criticized for thinking it is powerful, while in fact it is the LORD who is acting, using Assyria as a tool.
The LORD uses two rhetorical questions here to challenge Sennacherib. He answers them at the end of the verse.
Whom have you mocked and reviled?: This is the first question. The verbs mocked and reviled occurred earlier in this chapter (see the comments on verses 4 and 6). Here they both speak of the arrogant and offensive attitude of Sennacherib toward Yahweh.
Against whom have you raised your voice and haughtily lifted your eyes?: This second question is similar in meaning to the first one. Raised your voice seems to focus on an impolite or discourteous way of speaking to God rather than simply shouting at him. Haughtily lifted your eyes refers to an arrogant attitude (see 2.11). For this whole question Bible en français courant has “Against whom did you dare to speak and direct an arrogant look?”
Against the Holy One of Israel!: This is the LORD’s answer to the two questions. For the Holy One of Israel, see the comments on 1.4.
Good News Translation changes the second question into a strong statement. It appears as a response to the first question. Good News Translation also refers to the LORD in the first person since he is speaking by saying “… to me, the holy God of Israel.” Contemporary English Version uses a strong statement for both questions: “Sennacherib, you cursed, shouted, and sneered at me, the holy God of Israel.” Other translation examples for this verse are:
• “Whom have you mocked and scorned?
Whom have you shouted at and acted arrogantly against?
None other than the Holy One of Israel!
• “It is the Holy One of Israel you have mocked and scorned.
You have spoken disrespectfully to him and acted arrogantly against him.
• “Whom have you mocked and blasphemed?
Against whom have you spoken so loudly,
and whom have you treated with such disdain?
You have done these things against [me,] Israel’s Holy One!
Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .