Herod had arrested Peter and imprisoned him. Yet despite his dangerous situation Peter was very calm, even although it was likely that he would be executed soon.
So why was Peter calm? I would suggest he was in such a state because he expected that the prediction of his death by Jesus was about to be fulfilled. Jesus had told Peter that the day would come when he would be put to death (John 21) and it is reasonable to assume that Peter would have imagined that now was the time of fulfilment. It is amazing the degree of calmness that comes from a focus that knows that Jesus is in control.
What can we say about is rescue of Peter by the angel. We should note first that no political power can do anything against Christ’s church unless he allows it. To Herod’s eyes, Peter and James seemed equal prey. In heaven’s eyes, Herod would not be able to do anything against Peter. We should remember this reality at all times.
Further, we should also observe that often divine rescues come late in the day. It is almost as if the Lord waits until his opponents have done all they can. Here is Peter, chained and guarded, unable to move far. Any observer would deduce that he was finished, apart from heavenly observers. They would know that their Master plans his rescues in such a way that exalts his timing and exposes the weakness of his enemies. This is what happened here, and as it was then, so it is the case now. No power on earth can prevent God from doing what he wishes.
Moreover, we can see that the angel did not do for Peter what he could do for himself. Peter was told to dress himself and to walk. This is a clear principle in the Bible. The Lord will not do for us what we should do ourselves. I think we would like him to do everything in evangelism and in providing spiritual company. Yet if it is within our power to provide it, we must perform it in order to know the Lord’s blessing. Of course, the things we cannot do, the Lord will do for us, similar to how he took care of loosening the chains and opening the prison door.