God did not tell Peter that all foods are permissible! Unclean foods are still not permissible today. Jesus did not eat unclean foods, neither did the disciples, including after Jesus rose from the dead.
The unclean foods in Peter's vision represented Gentiles, and the message was that salvation was for all men, Jew and Gentile, the "clean and the unclean." Scripture explains what Peter's vision meant:
(From Acts 10)
27While talking with him, Peter went inside and found a large gathering of people.
28He said to them: “You are well aware that it is against our law for a Jew to associate with or visit a Gentile. But God has shown me that I should not call anyone impure or unclean.
29So when I was sent for, I came without raising any objection. May I ask why you sent for me?”
30Cornelius answered: “Three days ago I was in my house praying at this hour, at three in the afternoon. Suddenly a man in shining clothes stood before me
31and said, ‘Cornelius, God has heard your prayer and remembered your gifts to the poor.
32Send to Joppa for Simon who is called Peter. He is a guest in the home of Simon the tanner, who lives by the sea.’
33So I sent for you immediately, and it was good of you to come. Now we are all here in the presence of God to listen to everything the Lord has commanded you to tell us.”
34Then Peter began to speak: “I now realize how true it is that God does not show favoritism
35but accepts from every nation the one who fears him and does what is right.
36You know the message God sent to the people of Israel, announcing the good news of peace through Jesus Christ, who is Lord of all.
37You know what has happened throughout the province of Judea, beginning in Galilee after the baptism that John preached—
38how God anointed Jesus of Nazareth with the Holy Spirit and power, and how he went around doing good and healing all who were under the power of the devil, because God was with him.
39“We are witnesses of everything he did in the country of the Jews and in Jerusalem. They killed him by hanging him on a cross,
40but God raised him from the dead on the third day and caused him to be seen.
41He was not seen by all the people, but by witnesses whom God had already chosen—by us who ate and drank with him after he rose from the dead.
42He commanded us to preach to the people and to testify that he is the one whom God appointed as judge of the living and the dead.
43All the prophets testify about him that everyone who believes in him receives forgiveness of sins through his name.”
44While Peter was still speaking these words, the Holy Spirit came on all who heard the message.
45The circumcised believers who had come with Peter were astonished that the gift of the Holy Spirit had been poured out even on Gentiles.
46For they heard them speaking in tongues
band praising God.
Then Peter said,
47“Surely no one can stand in the way of their being baptized with water. They have received the Holy Spirit just as we have.”
