Acts 10 - 11 give the account of Peter's vision. In the dream, he, a Jew, is instructed to eat all kinds of creatures. He declines to do so, on account of these things being impure or unclean according to Old Testament laws. Then the same God who gave these laws, tells him not to call anything that God has made unclean. Shortly thereafter, some Gentiles arrive at his gate, having been sent by an angel.
It would appear that God has changed His mind here, or is at least indicating clearly that certain laws from before do not apply anymore. This frees Peter up to reach out to the Gentile visitors.
Might there be other things which God said before, which He does not want us to hold to anymore? And what if our reply is "You're crazy! That's not what the Bible says"?
Here's the full story:
About noon the following day as they were on their journey and approaching the city, Peter went up on the roof to pray. 10 He became hungry and wanted something to eat, and while the meal was being prepared, he fell into a trance. 11 He saw heaven opened and something like a large sheet being let down to earth by its four corners. 12 It contained all kinds of four-footed animals, as well as reptiles and birds. 13 Then a voice told him, “Get up, Peter. Kill and eat.”
14 “Surely not, Lord!” Peter replied. “I have never eaten anything impure or unclean.” 15 The voice spoke to him a second time, “Do not call anything impure that God has made clean.” 16 This happened three times, and immediately the sheet was taken back to heaven. 17 While Peter was wondering about the meaning of the vision, the men sent by Cornelius found out where Simon’s house was and stopped at the gate. 18 They called out, asking if Simon who was known as Peter was staying there.
19 While Peter was still thinking about the vision, the Spirit said to him, “Simon, three[a] men are looking for you. 20 So get up and go downstairs. Do not hesitate to go with them, for I have sent them.”
21 Peter went down and said to the men, “I’m the one you’re looking for. Why have you come?”
22 The men replied, “We have come from Cornelius the centurion. He is a righteous and God-fearing man, who is respected by all the Jewish people. A holy angel told him to ask you to come to his house so that he could hear what you have to say.”
23 Then Peter invited the men into the house to be his guests.
Acts 10:9-23, NIV
For more on this, check out Darkwoodbrew Brew's episode on "For the love of God, pt 1: (Peter's Kosher) Pickle