Acts 10:9-16
The next day, as they were on their journey and coming near the city, Peter went up on the housetop to pray, about the sixth hour. And he became hungry and desired something to eat; but while they were preparing it, he fell into a trance and saw the heaven opened, and something descending, like a great sheet, let down by four corners upon the earth. In it were all kinds of animals and reptiles and birds of the air. And there came a voice to him, “Rise, Peter; kill and eat.” But Peter said, “No, Lord; for I have never eaten anything that is common or unclean.” And the voice came to him again a second time, “What God has cleansed, you must not call common.” This happened three times, and the thing was taken up at once to heaven.
To quote Fr Stephen De Young
"The thrust of this passage is to communicate to St. Peter that the Gentiles are no longer considered unclean, and that he can go into Cornelius’ home, and the Apostles in general can go to the Gentiles, without concern of becoming unclean through contact with Gentiles.
For this imagery to work and this message to be communicated, however, the core principle, that God has now made these animals, and the Gentiles, clean has to be true. The change here is not to the status of the commandments, but to the unclean status of the Gentiles and the various animals.
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