John Gill

They are enclosed in their own fat,.... Or "their fat has enclosed them"; either their eyes, that they can hardly see out of them, or their hearts, so that they are stupid and senseless, and devoid of the fear of God; the phrase is expressive of the multitude of their wealth and increase of power, by which they were swelled with pride and vanity, and neither feared God nor regarded man; so the Targum paraphrases it, "their riches are multiplied, their fat covers them;'' see Deu 32:15; some read it, "their fat shuts their mouths", so Aben Ezra and Kimchi; or "with their fat they shut them" (h); but the accent "athnach" will not admit of this reading; the last word belongs to the next clause; with their mouth they speak proudly; against God and his people, belching out blasphemies against the one, and severe menaces and threatenings against the other. (h) So De Dieu.