"No, Lord!"

This was Peter's response when he thought the vision he received in Acts 10 was about eating unclean animals.

13 Then a voice said to him, “Get up, Peter; kill and eat!”

14 “No, Lord!” Peter said. “For I have never eaten anything common and ritually unclean!” (Acts 10)

Let that sink in for a moment.  This disciple who walked with Jesus hearing all of his teachings first-hand is appalled at the notion of eating unclean animals.   Surely if Jesus was planning for his followers to disregard Father's commandments Peter would have known about it. 

Instead, Peter was clear that he has never eaten unclean animals and was so adamant that he refused the instruction given from Jesus in the vision.

Then the voice says:
15 Again, a second time, a voice said to him, “What God has made clean, you must not call common.”

Afterwards, Peter was still perplexed at what the vision could mean:

17 While Peter was deeply perplexed about what the vision he had seen might mean, the men who had been sent by Cornelius, having asked directions to Simon’s house, stood at the gate.

The men sent by Cornelius were now at the gate.  They were sent because an angel of God had so instructed Cornelius in Acts 10:1-8.

The Spirit told Peter to go with these men:

19 While Peter was thinking about the vision, the Spirit told him, “Three men are here looking for you. 20 Get up, go downstairs, and accompany them with no doubts at all, because I have sent them.”

In the following verses, Acts 10:21-27, the three men explain why they are there.  Peter invites them in and returns with them the next day. 

Cornelius was expecting Peter and had many relatives and friends there awaiting his arrival.  When Peter arrived he said to them:

28 Peter said to them, “You know it’s forbidden for a Jewish man to associate with or visit a foreigner. But God has shown me that I must not call any person common or unclean.

This is where we get to the meat of the matter.  Peter shares the meaning of his vision which is that he must not call any person common or unclean.  Who forbade Jewish men from associating with foreigners?  It wasn't God.  It was a Jewish man-made tradition related to the one I discussed here: Disregarding the command of God, you keep the tradition of men.

Peter goes on to explain that this is why he came as requested:

29 That’s why I came without any objection when I was sent for. So I ask: Why did you send for me?”

Cornelius answers by explaining how he was visited by the angel and told to request Peter.  Peter responds with all of the good news:  Acts 10:30-47.

In the next chapter of Acts, Peter summarizes the whole ordeal.  It's clear the meaning of the vision is about going with the 'unclean' men and not about eating unclean animals:

11 The apostles and the brothers who were throughout Judea heard that the Gentiles had welcomed God’s message also. 2 When Peter went up to Jerusalem, those who stressed circumcision argued with him,3 saying, “You visited uncircumcised men and ate with them!”4 Peter began to explain to them in an orderly sequence, saying: 5 “I was in the town of Joppa praying, and I saw, in a visionary state, an object that resembled a large sheet coming down, being lowered by its four corners from heaven, and it came to me. 6 When I looked closely and considered it, I saw the four-footed animals of the earth, the wild beasts, the reptiles, and the birds of the sky. 7 Then I also heard a voice telling me, ‘Get up, Peter; kill and eat!’8 “‘No, Lord!’ I said. ‘For nothing common or ritually unclean has ever entered my mouth!’ 9 But a voice answered from heaven a second time, ‘What God has made clean, you must not call common.’10 “Now this happened three times, and then everything was drawn up again into heaven. 11 At that very moment, three men who had been sent to me from Caesarea arrived at the house where we were. 12 Then the Spirit told me to accompany them with no doubts at all. These six brothers accompanied me, and we went into the man’s house. 13 He reported to us how he had seen the angel standing in his house and saying, ‘Send to Joppa, and call for Simon, who is also named Peter. 14 He will speak a message to you that you and all your household will be saved by.’15 “As I began to speak, the Holy Spirit came down on them, just as on us at the beginning. 16 Then I remembered the word of the Lord, how He said, ‘John baptized with water, but you will be baptized with the Holy Spirit.’ 17 Therefore, if God gave them the same gift that He also gave to us when we believed on the Lord Jesus Christ, how could I possibly hinder God?”18 When they heard this they became silent. Then they glorified God, saying, “So God has granted repentance resulting in life even to the Gentiles!”

Notice that at no time does Peter change his disgust at the notion of eating unclean animals, but he does change his mind about the man-made tradition about associating with Gentiles. 

Many have taken some of these verses out of context in an effort to justify their sin of eating unclean.  The reality, however, is that the context disproves their claim and actually proves quite the opposite.