Acts of the Apostles 12:4-6

Then he imprisoned him, placing him under the guard of four squads of four soldiers each. Herod intended to bring Peter out for public trial after the Passover. But while Peter was in prison, the church prayed very earnestly for him. The night before Peter was to be placed on trial, he was asleep, fastened with two chains between two soldiers. Others stood guard at the prison gate.