Peter therefore was kept in prison. But prayer was made without ceasing by the church unto God for him.  And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison.
 And behold an angel of the Lord stood by him: and a light shined in the room: and he striking Peter on the side, raised him up, saying: Arise quickly. And the chains fell off from his hands.  And the angel said to him: Gird thyself, and put on thy sandals. And he did so. And he said to him: Cast thy garment about thee, and follow me.  And going out, he followed him, and he knew not that it was true which was done by the angel: but thought he saw a vision.  And passing through the first and the second ward, they came to the iron gate that leadeth to the city, which of itself opened to them. And going out, they passed on through one street: and immediately the angel departed from him.
-- Acts of the Apostles 12:5-10