John Chrysostom

"And there came a voice to him, Rise, Peter; kill, and eat." "Rise, Peter," saith the Voice, "kill and eat." Probably he was on his knees when he saw the vision.

Homily on Acts 22 ↗

Theophylact of Ohrid

Everyone would have begun to accuse Peter as a lawbreaker, and therefore it is arranged by the Spirit so that he would have a defense; that is why he objects to the Angel. For he had to fully observe the law. So this is arranged so that they would not begin to accuse him. Perhaps, having knelt down, he saw the vision. And what happened was a Divine act, that is, that he saw things above and was in a state of ecstasy, and heard a voice from there. …

Commentary on Acts ↗

Oecumenius

Perhaps kneeling he had seen the vision: therefore the voice also said to him, "Rise, Peter, kill and eat." But it showed that what he had seen was divine by reason of his being raised into a trance of mind, and because the voice descended from there, and because on the third time it declared that it was unclean. Moreover, that they came from heaven, and were withdrawn therefore, is a great argument of purification. This, however, was done for those about whom he was afterward to tell the matter. …

Commentary on Acts ↗

Bede

Rise, Peter, kill and eat. He says, rise to prepare for evangelization. Kill in the nations what they were, and make them what you are. For he who eats food outside takes it into his own body. Therefore, he commands that the nations placed outside through unbelief, with their past life killed, be incorporated into the society of the Church, which Peter signifies. According to what the Apostle Paul says about himself: For I through the law died to the law, that I might live to God and Christ. …

Commentary on Acts ↗