John Calvin Commentary Acts 26:13

"at midday, O king, I saw on the way a light from heaven, above the brightness of the sun, shining round about me and them that journeyed with me." — Acts 26:13 (ASV)

At midday, O king. The narration is intended to make King Agrippa understand that it was no empty vision or ghost, nor any kind of trance that drove him to madness and left him deprived of his judgment. For although he fell to the ground in fear, he still heard a clear voice; he asked who it was that spoke; he understood the answer that was given—all of which are signs that he was not out of his mind. Therefore, it follows that he did not impulsively change his mind, but rather devoutly and holily obeyed the heavenly oracle, lest he intentionally persist in striving against God.