Acts 11:1 - 3

"The apostles and the brothers throughout Judea heard that the Gentiles also had received the word of God. So when Peter went up to Jerusalem, the circumcised believers criticized him and said, 'You went into the house of uncircumcised men and ate with them.'" NIV translation

When God moves, people learn of it and that is what happened after the events of chapter ten. The idea that God loved non-Jewish people would have caused a big stir. Therefore, when Peter went to Jerusalem, the Jews accused him of breaking the law as it was against the Mosaic Law for Jew to associate with a Gentile.

Acts 11:4 - 15

Peter recounts the events from chapter ten.

Acts 11:16 & 17

"Then I remembered what the Lord had said: 'John baptized with water, but you will be baptized with the Holy Spirit.' So if God gave them the same gift as he gave us, who believed in the Lord Jesus Christ, who was I to think that I could oppose God?" NIV translation

After telling the story of the message that God had given him, Peter reasoned with the church leaders. His reasoning was that, if God wanted to do something such as sharing the gospel with the Gentiles, who was he to oppose that will.

Acts 11:18

"When they heard this, they had no further objections and praised God, saying, 'So then, god has granted even the Gentiles repentance unto life.'" NIV translation

Upon hearing Peter's testimony and reasoning, the religious leaders understood that it was a "God thing" and not of man. They chose to accept the will of God and put their traditions and prejudices aside which is a good lesson for us today as well.