John Calvin Commentary Daniel 2:26

"The king answered and said to Daniel, whose name was Belteshazzar, Art thou able to make known unto me the dream which I have seen, and the interpretation thereof?" — Daniel 2:26 (ASV)

The king says these words out of his despair of any interpretation, since he perceived that all the Magi, in this matter, lacked judgment and understanding. He was initially convinced that only the Magi possessed wisdom. Since he had questioned them without success, the error he was filled with, as I have mentioned, prevented him from hoping for anything better from any other source. Therefore, out of surprise, he asks here, as if it were impossible, Have you that power?

There is no doubt that God drew this question from the proud king to make His grace in Daniel more illustrious. The less hope the king himself had, the more dignity and reverence the revelation consequently possessed, as we will see later; for the king was astonished and, in a stupor, fell prostrate on the ground before a captive! This is the reason why the shrewd Daniel recounts the king asking this question.