And they said unto her, Thou art mad. But she constantly affirmed that it was even so. Then said they, It is his angel.

People's New Testament

12:15 It is his angel. The Jews held that every one had his guardian angel, and the thought his angel had assumed Peter's voice. A mistake, and Luke does not say whether the idea on which it was based is true or not.

Wesley's Notes

12:15 They said, Thou art mad - As we say, Sure you are not in your senses to talk so. It is his angel - It was a common opinion among the Jews, that every man had his particular guardian angel, who frequently assumed both his shape and voice. But this is a point on which the Scriptures are silent.

Jamieson-Fausset-Brown Bible Commentary

15. Thou art mad-one of those exclamations which one can hardly resist on hearing what seems far "too good to be true."

she constantly affirmed-"kept steadfastly affirming."

that it was even so. Then said they, It is his angel-his disembodied spirit, his ghost; anything, in fact, rather than himself. Though this had been the burden of their fervent prayers during all the days of unleavened bread, they dispute themselves out of it as a thing incredible. Still, it is but the unbelief of the disciples who "believed not for joy and wondered" at the tidings of their Lord's resurrection. How often do we pray for what we can hardly credit the bestowment of, when it comes in answer to our prayers! This, however, argues not so much hard unbelief as that kind of it incident to the best in this land of shadows, which perceives not so clearly as it might how very near heaven and earth, the Lord and His praying people, are to each other.

Matthew Henry's Concise Commentary

12:12-19 God's providence leaves room for the use of our prudence, though he has undertaken to perform and perfect what he has begun. These Christians continued in prayer for Peter, for they were truly in earnest. Thus men ought always to pray, and not to faint. As long as we are kept waiting for a mercy, we must continue praying for it. But sometimes that which we most earnestly wish for, we are most backward to believe. The Christian law of self-denial and of suffering for Christ, has not done away the natural law of caring for our own safety by lawful means. In times of public danger, all believers have God for their hiding-place; which is so secret, that the world cannot find them. Also, the instruments of persecution are themselves exposed to danger; the wrath of God hangs over all that engage in this hateful work. And the range of persecutors often vents itself on all in its way.