The greatnesss and suddenness of the deliverance was such, as it amazed him, it seemed incredible unto him: not that he questioned God's power or godliness; but knowing that he was to suffer for Christ's name's sake, he might the rather not look for such a deliverance, and when it came, be as one that dreams, as Psalms 126:1: God therefore bringing his people to such extremities, that his salvation might be the more astonishing.
Related Commentaries of Acts 12:9
Acts 12:9
9 And he went out, and followed him; and wist not that it was true which was done by the angel; but thought he saw a vision.