Albert Barnes Commentary Daniel 2:29

"as for thee, O king, thy thoughts came [into thy mind] upon thy bed, what should come to pass hereafter; and he that revealeth secrets hath made known to thee what shall come to pass." — Daniel 2:29 (ASV)

As for you, O king, your thoughts came into your mind upon your bed — Margin, “up;” that is, your thoughts ascended. The Chaldee is, “your thoughts ascended” — סלקוּ selı̂qû. So the Greek: “Your thoughts ascended (ἀνέβησαν anebēsan) upon your couch.” There is, evidently, some allusion to the thoughts “ascending,” or “going up;” and perhaps the idea is, that they were employed on important subjects — an idea which we now express by saying that one’s thoughts are “elevated,” as contrasted with those which are “low” and “grovelling.”

What should come to pass hereafter — It would seem most probable from this, that the thoughts of Nebuchadnezzar were occupied with this subject in his waking moments on his bed, and that the dream was grafted on this train of thought when he fell asleep. Nothing is more probable than that his thoughts might be thus occupied. The question respecting his successor; the changes which might occur; the possibility of revolutions in other kingdoms, or in the provinces of his own vast empire, all were topics on which his mind would probably be employed.

As God designed, too, to fix his thoughts particularly on that general subject—the changes which were to occur in his empire—such an occasion, when his attention was greatly engrossed with the subject, would be very suitable to impart the knowledge which he did by this vision. Daniel refers to this, probably, because it would do much to confirm the monarch in the belief of his inspiration, if he referred to the train of thought which had preceded the dream; as it is not improbable that the king would remember his “waking” thoughts on the subject, though his “dream” was forgotten.