Acts 16:20-26

and when they had brought them before the chief magistrates, they said, “These men, who are Jews, are throwing our city into confusion and causing trouble. They are publicly teaching customs which are unlawful for us, as Romans, to accept or observe.” The crowd also joined in the attack against them, and the chief magistrates tore their robes off them and ordered that Paul and Silas be beaten with rods. [2 Cor 11:25] After striking them many times [with the rods], they threw them into prison, commanding the jailer to guard them securely. He, having received such a [strict] command, threw them into the inner prison (dungeon) and fastened their feet in the stocks [in an agonizing position]. But about midnight when Paul and Silas were praying and singing hymns of praise to God, and the prisoners were listening to them; suddenly there was a great earthquake, so [powerful] that the very foundations of the prison were shaken and at once all the doors were opened and everyone’s chains were unfastened.