John Gill Commentary Isaiah 29:4

"And thou shalt be brought down, and shalt speak out of the ground, and thy speech shall be low out of the dust; and thy voice shall be as of one that hath a familiar spirit, out of the ground, and thy speech shall whisper out of the dust." — Isaiah 29:4 (ASV)

And you shall be brought down
To the ground, and laid level with it, even the city of Jerusalem, as it was by the Romans; and as Christ predicted it would be (Luke 19:44). Though some understand this as the humbling of its inhabitants by the appearance of Sennacherib's army before it, interpreting the following clauses in that light:

[and] shall speak out of the ground, and your speech shall be low
out of the dust ; Some explain this of the submissive language of Hezekiah to Sennacherib, and of his messengers to Rabshakeh (2 Kings 18:14, 2 Kings 18:26), as Aben Ezra and Kimchi. But it is expressive of the great famine in Jerusalem at the time of its siege by the Romans, when the inhabitants were so reduced by it that they were scarcely able to speak so as to be heard, and could not stand upon their legs, but fell to the ground and lay in the dust, uttering from there their speech with a faint and feeble voice:

and your voice shall be as one that has a familiar spirit, out of
the ground, and your speech shall whisper out of the dust : or peep and chirp, as little birds, as Jarchi and Kimchi say, as those did that had familiar spirits; and as the Heathen oracles were delivered, as if they came out of the bellies of those who spoke, or out of caves and hollow places in the earth. And this was in just retaliation to these people, who imitated such practices and made use of such spirits; see (Isaiah 8:19).