Charles Ellicott Commentary Revelation 20:3

"and cast him into the abyss, and shut [it], and sealed [it] over him, that he should deceive the nations no more, until the thousand years should be finished: after this he must be loosed for a little time." — Revelation 20:3 (ASV)

And cast him into the bottomless pit...—Rather, and cast him into the abyss (same word as in Revelation 20:1), and locked and sealed (the door or mouth) above him, that he may not deceive the nations any more until the thousand years shall have been finished; after these things he must be loosed for a little time.

The sealing reminds us of the sealing employed when the wicked one had power through human agency to imprison God’s messengers. (Compare Daniel 6:17, and Matthew 27:66.) Of the exact moment when this binding and imprisoning took place, it is not necessary to inquire too closely. What in the vision is described as the work of a moment may, in fact and fulfillment, be a very gradual work; or rather, the full manifestation of its accomplishment may only gradually be made clear.

Therefore, to fix it to any incident (for example, as Hengstenberg is disposed to do regarding the coronation of Charlemagne), is to fall into the “vicious realism” against which he rightly protests. The same applies to the duration of the imprisonment; it is not to be understood literally any more than the other numbers in the book; it symbolizes a lengthened period. This period is followed by the devil being loosed again for a short time. (See Note on Revelation 20:7.)