Acts 12:5-7 (NIV)
5 So Peter was kept in prison, but the church was earnestly praying to God for him.
6 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.
7 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.