Albert Barnes Commentary Isaiah 48:15

"I, even I, have spoken; yea, I have called him; I have brought him, and he shall make his way prosperous." — Isaiah 48:15 (ASV)

I, even I, have spoken – The word ‘I’ is repeated to give emphasis and to provide the utmost security that it would certainly be accomplished. It means that Yahweh, and he alone, had declared this, and that it was entirely by his power that Cyrus had been raised up and had been made prosperous.

Yea, I have called him – (See the note at Isaiah 41:2).

I have brought him – I have led him on his way in his conquests.

And he shall make his way prosperous – There is a change of person in this verse, from the first to the third, which is quite common in the writings of Isaiah.