Matthew Poole and continuators on 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.

The greatness and suddenness of the deliverance, was such, as it amazed him, it seemed incredible unto him; not that he questioned Gods power or goodness; but knowing that he was to suffer for Christs name sake, he might the rather not look for such a deliverance, and when it came, be as one that dreams, as Psal. 126.1. God therefore bringing his people to such extremities, that his Salvation might be the more astonishing.