Daniel 2:29

The one who interprets what another has seen is more a prophet than the one who had seen.… Less a prophet is he who … sees in spirit only the signs of the things signified, and a greater prophet is he who is granted only an understanding of images. But the greatest prophet is he who is endowed with both gifts, namely, that of seeing in spirit the symbolic likeness of corporeal objects and that of understanding them with the vital power of the mind. Such a one was Daniel. His preeminence was tested and established when he not only told the dream he had had but also explained the meaning of it. For the corporeal images themselves were produced in his spirit, and an understanding of them was revealed in his mind. I am using the word spirit, therefore, in the sense in which Paul uses it, where he distinguishes it from the mind: "I will pray with the spirit, but I will pray with the mind also." Here he implies that signs of things are formed in the spirit and that an understanding of the signs shines forth in the mind.

For after the king had taken Egypt and after taking over the Jewish land and deporting the people, he considered upon his bed what was there to do after these things. But he who knows the secrets of all and searches the considerations of the hearts, revealed to the king what will be through the image, but God hid the vision from him, so that the plans of God would be able to be explained not by the wise men of Babylon, but by the blessed Daniel, in as much as the things which were hidden from all, were revealed by the prophet of God.

"Thou, O king, diddest begin to think in thy bed, what should happen in times to come; and he that revealeth mysteries did shew thee what things should come:" and a little after: "Thou diddest see, and behold as it were a great statue." Wherefore, seeing Daniel doth with reverence insinuate that the dream should come to pass, and also declareth from what cogitation it did spring, plainly do we learn that dreams sometimes do come both of thought and revelation together. But seeing dreams do grow from such divers roots, with so much the more difficulty ought we to believe them: because it doth not easily appear unto us, from what cause they do proceed. Holy men, indeed, by a certain inward spiritual taste, do discern betwixt illusions and true revelations, by the very voices or representations of the visions themselves: so that they know what they receive from the good spirit, and what they suffer by illusion from the wicked: and therefore, if our mind be not herein very attentive and vigilant, it falleth into many vanities, through the deceit of the wicked spirit: who sometime useth to foretell many true things, that, in the end, he may by some falsehood ensnare our soul. As not long since it is most certain, that it befell to one that lived amongst us, who, being much given to observe dreams, had one night in a dream long life promised him: and when as he had made provision of great store of money for the maintenance of his many days, he was so suddenly taken out of this life, that he left it all behind him, without ever having any use thereof, and carried not with him any good works to the next world.

As for thee, O king,....

Just before he fell asleep, and dreamed this dream, he was musing in his own mind what would be the issue of his growing greatness, what his kingdom would hereafter come to; and so the dream was an answer to those thoughts.