John Calvin on Acts 26:13-15

13. At midday, O king. The narration tendeth to this end, that king Agrippa may understand that it was no vain visure or ghost, neither was it any such trance as brought him into some madness, so that he was destitute of judgment. “Quae mentis sanitatem vel judicium illi eriperet,” as deprived him of his sober senses, or the power of judging. For though he fell to the earth for fear, yet he heareth a plain voice; he asketh who it was that spake; he understandeth the answer which was made, which are signs that he was not beside himself. Hereupon it followeth that he did not rashly change his mind, but did godlily and holily obey the heavenly oracle, lest he should of set purpose proceed to strive against God.