What does Acts 16:27 mean?

When Herod Agrippa I imprisoned Peter with the intent to execute him, God sent an angel to lead Peter out of the prison. Because they let a prisoner go free, Agrippa had the guards executed (Acts 12:3–19). When a jailer in Philippi realizes a freak earthquake has opened all his cell doors and unloosed his prisoners' chains, he prepares to kill himself. He is personally responsible for the prisoners of the Roman outpost. A sword is kinder than what the city magistrates would do to him; they might even crucify him.

Among the prisoners are Paul and Silas. Hours before, the magistrates had beaten and imprisoned them for breaking the law by promoting a new religion: the worship of Jesus of Nazareth. They spent the early hours praying and singing hymns while the other prisoners listened. It's not written, but likely they influenced their cell mates to stay (Acts 16:20–25).

When the jailer finds none of the prisoners escaped, he is overwhelmed. He falls at Paul and Silas's feet and asks them how to be saved. They tell him and his household about Jesus; they believe and are baptized. He then dresses their wounds and feeds them, no longer concerned about what the magistrates may think (Acts 16:28–34).

Of course, Paul and Silas trust God for their well-being, whether God's will includes freedom or eternity in Jesus' presence. But they have an ace up their sleeves. Although the charges against them are true, their punishment was illegal. They are Roman citizens, which even in that era meant a right to "due process:" a controlled process before punishment. They had been beaten and imprisoned without a fair trial. When the magistrates find out, they fear for their own lives. Paul and Silas demand an official apology and agree to leave (Acts 16:35–40). But the jailer and his family are forever changed.