Bede : Because I have never eaten anything common and unclean. The people of the Jews, boasting themselves as part of God, call common foods those which all men use. For example, pork, oysters, hares, and such animals which do not split the hoof, nor chew the cud, nor have scales among fish. But unclean foods are said to be the flesh of beasts or reptiles, which are not edible by any mortals. — Commentary on Acts Clement of Alexandria : Peter abstained from swine; "but a trance fell on him," as is written in the Acts of the Apostles, "and he saw heaven opened, and a vessel let down on the earth by the four corners, and all the four-footed beasts and creeping things of the earth and the fowls of heaven in it; and there came a voice to him, Rise, and slay, and eat. And Peter said, Not so, Lord, for I have never eaten what is common or unclean. And the voice came again to him the second time, What God hath cleansed, call not thou common." The use of them is accordingly indifferent to us. "For not what entereth into the mouth defileth the man," but the vain opinion respecting uncleanness. — The Instructor Book 2 Cyril of Alexandria : The law is spiritual and does not provide an explanation that stops at physical meanings. For while the holy Peter still desired to follow the customs of the Jews, and since he was trying to advance towards better things, yet because he was terribly overcome by his reverence for these figures, God sent down from heaven the linen filled with animals, which … were condemned figuratively by the decrees of the law as impure. He then ordered Peter to kill and, if he should choose, to eat. But the disciple was reluctant and spoke as a Jew: "Absolutely not, Lord, because I have never eaten anything that is common and unclean, and no impure meat has entered my mouth." So the voice of the Lord came down, not only because God was rebuking him but also he was saying clearly, "What God has cleansed, you must not call common." Then [Peter] immediately understood that the time had come when the shadows had to be transformed into truth. And so the passage of the figures into truth fulfilled them and should not show, as some people think, that they were placed there without a reason. Doubtless, the lawgiver does not consider a pig, or the other animals, now clean, now unclean. No, for he knows that they are well-made, for it is written, "And God saw all that he had made, and behold all was very good, and he blessed it." For to the extent that each thing of creation has come to be and to the extent that it has been made, it will only have, so I suppose, in itself what is good. So even though the pig cannot chew the cud, it is not unclean, but rather is perfectly edible, and what is proper to something's nature does not pollute it. As I have said, the law was figures and shadows that remained "until the time of correction." — AGAINST JULIAN 9.318-19 John Chrysostom : "But Peter said, Not so, Lord; for I have never eaten anything that is common or unclean." This was a thing altogether offensive to them: observe then what is providentially managed. He himself also says, "I have never eaten": not being himself afraid - far be the thought from us - but it is so contrived by the Spirit, in order that he may have it to say in answer to those accusing him, that he did object: for it was altogether necessary for them to observe the Law. He was in the act of being sent to the Gentiles: therefore that these also may not accuse him, see how many things are contrived by the Providence of God. For, that it may not seem to be a mere fancy, "this was done thrice. I said," saith he, "Not so, Lord, for I have never eaten aught common or unclean. And the voice came unto him, What God hath cleansed, that call not thou common." It seems indeed to be spoken to him, but the whole is meant for the Jews. For if the teacher is rebuked, much more these. — Homily on Acts 22 John Chrysostom : Wherefore did he object? That none may say that God was proving him, as in the case of Abraham, this is why he says, "Not so, Lord," etc. not gainsaying - just as to Philip also He said, "How many loaves have ye?" Not to learn, but tempting, or "proving him." And yet it was the same Lord that had discoursed above in the Law concerning things clean and unclean. But in that sheet were also "all the four-footed beasts of the earth," the clean with the unclean. — Homily on Acts 22 Tertullian : When, then, on being cursed, I smite (with my tongue, ) how shall I be found to have followed the doctrine of the Lord, in which it has been delivered that "a man is defiled, not by the defilements of vessels, but of the things which are sent forth out of his mouth. — Of Patience