Acts 11:1-5
Acts 11:1 (KJB)
And the apostles and brethren that were in Judaea heard that the Gentiles had also received the word of God.
Peter had understood correctly that he would definitely need witnesses to the events in Caesarea. It was heard that the Gentiles had received the Word of God, that is, that salvation was also preached among them. The early Jews in the church did not yet understand that the Gospel was now getting ready to make its way across the world from Jerusalem and they needed to have some things explained to them. Cornelius was a Roman Centurion and the Romans were occupying Israel at that time. This fact would have probably brought a lot of misunderstanding and maybe some accusations unless Peter explained to them. The Jews would never accept the fact that a Roman and a Jew could ever be on the same level because they counted Gentiles as inferior.
Acts 11:2 (KJB)
And when Peter was come up to Jerusalem, they that were of the circumcision contended with him,
Contended - Judge, dispute, or doubt
As soon as Peter had returned to Jerusalem, the Jews were waiting for him and started to dispute with him about the events in Caesarea. They did not even give Peter a chance to explain. At this time there were no uncircumcised Jews who became saved and were in the church. They had become saved right from Judaism and went right into the church. They were still holding to the old beliefs that the uncircumcised Gentiles could never become saved unless they were first circumcised. At this point Christianity was still new and those who kept the Mosaic law still preached that salvation could only happen if you are circumcised, so this would have been the source of contention.
Acts 11:3 (KJB)
Saying, Thou wentest in to men uncircumcised, and didst eat with them.
The Jews believes that if they went into the house of a Gentile, then they would be defiled. The leaders would not go into Pilateís judgment hall because they believed they would be defiled. (John 18:28 KJV) Then led they Jesus from Caiaphas unto the hall of judgment: and it was early; and they themselves went not into the judgment hall, lest they should be defiled; but that they might eat the passover. So the accusation came against Peter that he would have been unclean since he went into the house of a Gentile. They were also probably frightened that if the word got out that there were Gentiles in the church worshipping with Jews, it would bring the ire of the leaders down on the church and the peace they were experiencing would be gone.
Acts 11:4 (KJB)
But Peter rehearsed the matter from the beginning, and expounded it by order unto them, saying,
Peter knew there would be some type of opposition to what he did, so he did not condemn them nor did he chide them for they did not understand what had taken place. Peter then used the same method Stephen did and that was to give all the details by starting from the beginning and then go in order so there would be nothing missing from the story. This way they would have all the information without any breaches and by time he was done explaining they would understand that what transpired was of God and not of him.
Acts 11:5 (KJB)
I was in the city of Joppa praying: and in a trance I saw a vision, A certain vessel descend, as it had been a great sheet, let down from heaven by four corners; and it came even to me:
Peter then begins the narrative from the beginning stating how he was praying and then in the midst of his prayers, he saw a vision. That vision was a large sheet which descended from Heaven. Then when the sheet had descended, it did not move away from Peter but came toward him so he would be able to see everything and then understand the reason for this vision. Maybe there was concern for Peter thinking that he repudiated being a Jew but that was not the case as Peter would continue on and show that this vision had a great meaning for him and also for those who would be listening to him. A great lesson here, before we chide another believer, we must know how God may be working in that personís life and that we may not have all the facts yet. The Jews in Jerusalem did not have all the facts and they jumped to an early conclusion.