Who declared it from the beginning, that we might know, and beforehand, that we might say, “He is right”? There was none who declared it, none who proclaimed, none who heard your words.
26. Who hath declared from the beginning? Again the Lord attacks idols, after having maintained his divinity; for he asks if idolaters can produce anything of a similar nature to support their worship; that is, if they can bring forward any such instance of foreknowledge or power.
The Lord, by the prophet, here repeats the challenge to idolaters to make out the pretentions of their idols: "Produce your cause (Isa 41:21) and make your best of it; bring forth the strongest reasons you have to prove that your idols are gods, and worthy of your adoration." Note, There needs no more to show the absurdity of sin than to produce the reasons...
Commenting on Isaiah 41:21-29
Who hath declared from the beginning, that we may know?.... Who of the idols, or of their priests, that have declared things future before they came to pass, or ever predicted such an event as this before mentioned; which, if understood of Cyrus, was an hundred and fifty years before it came to pass; and if of Constantine, near a thousand years: and before time...