Acts 12:5

Peter therefore was kept in prison: but prayer was made without ceasing of the Church unto God for him. For the contest was now for life and death: both the slaying of the one made them fearful, and the casting of the other into prison.

Peter therefore was kept in prison. But this was all the better for Peter, who was thereby made more approved, and evinced his own manly courage. And it says, "there was earnest prayer making." It was the prayer of filial affection: it was for a father they asked, a father mild. "There was," it says, "earnest prayer." Hear how they were affected to their teachers. No factions, no perturbation: but they betook them to prayer, to that alliance which is indeed invincible, to this they betook them for refuge. They did not say, "What? I, poor insignificant creature that I am, to pray for him!" for, as they acted of love, they did not give these things a thought. And observe, it was during the feast, that their enemies brought these trials upon them, that their worth might be the more approved.

So Peter was kept in the prison. They, being at large, were at prayer: he, bound, was in sleep.