Gevurot Meyruach Hakodesh 16:25-26

And about chatzot halailah Rav Sha'ul and Sila were davening and were singing niggunim to HASHEM, and the prisoners were listening to them. And, suddenly, there came a gevaltike earthquake, so that the beis hasohar was shaken to its foundations, and immediately were opened all delatot (doors) and all sharsherot (chains) were unfastened.