The Acts 12:4-6

And when he had apprehended him, he cast him into prison, delivering him to four files of soldiers to be kept, intending, after the pasch, to bring him forth to the people. 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.