In the third year of the reign of king Belshazzar - In regard to Belshazzar, see Intro. to Daniel 5 Section II.
A vision appeared unto me - This vision appears to have occurred to him when awake, or in an ecstasy; the former one occurred when he was asleep, Daniel 7:1. Compare Daniel 8:17-18, where the prophet represents himself as overpowered, and as falling down to the earth on account of the vision. The representation would seem to have been made to pass before his mind in open day, and when he was fully awake. Compare the case of Balaam, Numbers 24:4 : “Which saw the vision of the Almighty, falling into a trance, but having his eyes open.”
After what appeared unto me at the first - That occurred in the first year of Belshazzar, Daniel 7:1.