John Calvin Commentary Acts 12:7

"And behold, an angel of the Lord stood by him, and a light shined in the cell: and he smote Peter on the side, and awoke him, saying, Rise up quickly. And his chains fell off from his hands." — Acts 12:7 (ASV)

A light shined. It is thought that Peter alone saw this light, and that the soldiers either slept so soundly or were so amazed that they neither felt nor perceived anything.

There might be two reasons why God would have the light shine: either so that Peter might have the use of it and the darkness might not be a hindrance to him, or that it might be for him a sign and token of heavenly glory.

For we often read that angels appeared with glistening brightness, even when the sun was shining. Surely, Peter might have gathered from the strange light that God was present, and he also ought to have profited from it.

When the angel strikes Peter’s side, it appears from this what care God has for His own, who watches over them when they sleep and raises them when they are drowsy.

And surely, we would be most miserable if the continuance of our prayers alone kept God watching over us; for such is the weakness of our flesh that we faint and quail, and we are most in need of His help when our minds, being distracted, do not seek Him.

Sleep is a kind of image of death, and chokes and drowns all the senses. What would become of us if God should then cease to care for us? But because when the faithful go to sleep, they commit their safety to God, it happens by this means that even their sleep calls upon God.

When he says that immediately after the angel had spoken the word the chains were loosed, we gather from this that there is power enough in the commandment of God alone to remove all kinds of hindrances, when all ways seem to be blocked on all sides.

So, if He intends to appease the movements and tumults of war, although the whole world were arrayed in armor, their spears and swords will immediately fall from their hands.

On the other hand, if He is determined to punish us and our sins with war, in a moment (in the twinkling of an eye), their minds, which were previously inclined to peace, will grow hot, and they will take up their swords.

Since Luke sets down separately both the words of the angel and also the course of events, it serves for the greater certainty of the history, so that it may in every respect appear that Peter was delivered by God.