Luke points out that, not just were Paul and Silas praying and singing, the prisoners were listening to them. They connected the dots between the prayers and singing and the earthquake. They were quick to follow their lead in staying when their chains fell off.
The jailer was essentially saved twice. After he was spared falling on his sword, the jailer asked, "What must I do to be saved?" I want people to ask me that question. I'm sure his was prompted not just by the earthquake, but by the fact they stayed in the jail. What do I need to do to prompt that question? What if it means staying in jail?
Paul refused to be let go quietly. Was he just belligerent or was he following the Spirit's leading? Should I follow him in this kind of self-defense, or should I let it go?