Acts 12:4-8 NIV
After arresting him, he put him in prison, handing him over to be guarded by four squads of four soldiers each. Herod intended to bring him out for public trial after the Passover.
So Peter was kept in prison, but the church was earnestly praying to God for him.
The night before Herod was to bring him to trial, Peter was sleeping between two soldiers, bound with two chains, and sentries stood guard at the entrance. Suddenly an angel of the Lord appeared and a light shone in the cell. He struck Peter on the side and woke him up. “Quick, get up!” he said, and the chains fell off Peter’s wrists.
Then the angel said to him, “Put on your clothes and sandals.” And Peter did so. “Wrap your cloak around you and follow me,” the angel told him.
NIV: New International Version