I have declared the former things - That is, in former times I have predicted future events by the prophets, which have come to pass as they were foretold. Though the fulfillment might have appeared to be long delayed, yet it came to pass at the very time, showing it to be an exact fulfillment of the prophecy. The design of thus referring to the former predictions is, to remind them of their proneness to disregard his declarations, and to recall to their attention the fact that all that he said would be certainly accomplished. As a people, they had been prone to disbelieve his word. He saw that the same thing would take place in Babylon, and that there also they would disbelieve his prophecies about raising up Cyrus, and restoring them to their own land. He therefore endeavors to anticipate this, by reminding them of their former unbelief, and of the fact that all that he had foretold in former times had come to pass.
From the beginning - In regard to this, and the meaning of the phrase, ‘the former things, see the notes at Isaiah 41:22; Isaiah 43:9. The phrase. ‘former things,’ refers to the things which precede others; the series, or order of events.
I did them suddenly - They came to pass at an unexpected time; when you were not looking for them, and when perhaps you were doubting whether they would occur, or were calling in question the divine veracity. The idea is, that God in like manner would, certainly, and suddenly, accomplish his predictions about Babylon, and their release from their captivity.