And I heard also a voice saying to me, “Rise, Peter; kill and eat.” But I said, “Not so, Lord: for nothing common or unclean has ever entered into my mouth.” But a voice answered the second time out of heaven, “What God has cleansed, you must not make common.” And this was done three times, and all were drawn up again into heaven.”
Then he described how three times God had called on him to eat, and how three times he had refused because he had considered that such things were unholy and unclean. And then he explained how three times God had rebuked him and declared, ‘What God has cleansed you must not make common.' Note the verb ‘make'. The point was that Peter was trying to make common again what God had cleansed and made holy, for God can cleanse what He will. Thus God had made clear that somehow these creatures coming down from heaven, which would normally be seen as unclean, were not to be seen as unclean or unholy, and the reason was because God had cleansed them. They came from God, from heaven. How could they be unclean?