It is his angel.— Many commentators understand this as if they had said, "It is his messenger, or one sent from him;" and it is certain that the word Αγγελος has frequently this sense in the scripture; but as the maid averred that she knew his voice, and was assured that it was Peter himself, it seems clear that they judged it to be something supernatural. Possibly they might imagine that it was an angel who assumed his form, to bring them some tidings of him; or that he had been executed in prison, as John the Baptist was, in the night, and that his separate spirit appeared as a token of its being employed, asangels are, in ministering to the church on earth. See Matthew 18:10. It is by no means certain that they imagined this to be his guardian angel; for Philo speaks of it as a received notion among the Jews, that the souls of good men deceased officiated as ministering spirits.
Related Commentaries of Acts 12:15
Acts 12:15
15 And they said unto her, Thou art mad. But she constantly affirmed that it was even so. Then said they, It is his angel.