16 But Peter continued knocking: and when they had opened the door, and saw him, they were astonished.

...they could not believe their senses when Peter presented himself at the door. It is human weakness. The saints of the nineteenth century may hope to have their own joyful experience of this shortly, when after praying for a lifetime for the Lord's coming amid increasing human frailty, and, it may be, faltering expectation, the angel of his presence will announce that the prayer is answered to the joy of thousands, who will only find suitable vent to their feelings in tears.

Nazareth Revisited Ch 4