About midnight, while Paul and Silas were praying and singing hymns to God as the prisoners listened, there was suddenly such a severe earthquake that the foundations of the jail shook; all the doors flew open, and the chains of all were pulled loose. (Acts 16:25-26)

When I visited Spain, we saw churches with chains attached to their exterior. The chains were from Christian prisoners who had been freed during the reconquest or had been redeemed from their captors.