John Calvin Commentary Acts 12:5

"Peter therefore was kept in the prison: but prayer was made earnestly of the church unto God for him." — Acts 12:5 (ASV)

But prayers were made. Luke teaches here that the faithful did not, in the meantime, neglect their duty. Peter stood in the forefront alone, but all the rest fought with their prayers together with him, and they aided him as much as they could. From this we also gather that they were not discouraged, for by prayer they testify that they persist as much as they are able in defense of the cause for which Peter was in danger of his life.

This passage teaches, first, how we ought to be affected when we see our brethren persecuted by the wicked for the testimony of the gospel. For if we are slothful, and if we are not inwardly touched with their dangers, we not only deny them the duty of love owed to them, but also treacherously forsake the confession of our faith. And, assuredly, if the cause is common, indeed, if they fight for our safety and salvation, we not only forsake them, but even Christ and ourselves. And the present necessity requires that they be far more fervent in prayer than they commonly are, whoever will be counted Christians.

We see some of our brethren (being brought to extreme poverty) live in exile; others we see imprisoned, many cast into foul dungeons, many consumed with fire; indeed, we often see new torments invented, by which, being long tormented, they may experience death. Unless these provocations sharpen our desire to pray, we are more than foolish. Therefore, as soon as any persecution arises, let us at once betake ourselves to prayer.

Also, it is likely that the Church was more concerned about Peter’s life, because they would have suffered a great loss if he had departed. Nor does Luke say merely that prayer was made; but he also adds that it was earnest and continual, by which he helps us understand that the faithful prayed not coldly or superficially, but as long as Peter was in the conflict, the faithful did what they could to help him, and that without weariness. We must always understand that prayer is made to God (His name being invoked), which is what is expressed here, whenever mention is made of prayer in Scripture. For this is one of the chief and first principles of faith: that we ought to direct our prayers to God alone, as He claims for Himself this particular worship, Call upon me in the day of tribulation, (Psalms 50:15).