23 This verse alludes to the coming Assyrian invasion, when the people will hear a foreign language that sounds like gibberish to them. The Lord is the subject of the verb “will speak,” as v. 12 makes clear. He once spoke in meaningful terms, but in the coming judgment he will speak to them, as it were, through the mouth of foreign oppressors. The apparent gibberish they hear will be an outward reminder that God has decreed their defeat.
24 Heb “who said to them.”
25 This message encapsulates the Lord’s invitation to his people to find security in his protection and blessing.

In other versions

For by people of strange lips

and with a foreign tongue

the Lord will speak to this people,

to whom he has said,

“This is rest;

give rest to the weary;

and this is repose”;

yet they would not hear.

Very well then, with foreign lips and strange tongues

God will speak to this people,

to whom he said,

“This is the resting place, let the weary rest”;

and, “This is the place of repose”—

but they would not listen.

For he will speak to this people

with stammering speech

and in a foreign language.

He had said to them,

“This is the place of rest;

let the weary rest;

this is the place of repose.”

But they would not listen.

So now God will have to speak to his people

through foreign oppressors who speak a strange language!

God has told his people,

“Here is a place of rest;

let the weary rest here.

This is a place of quiet rest.”

But they would not listen.

For he will speak with stammering and another tongue to this people, to whom he has said,

“This is rest; give rest to the weary;

and this is repose”; yet they were not willing to hear.

For with stammering lips and another tongue

Will he speak to this people.

To whom he said,

This is the rest wherewith ye may cause the weary to rest;

And this is the refreshing: yet they would not hear.

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