12 And all the assembly fell silent, and they listened to Barnabas and Paul as they related what signs and wonders God had done through them among the Gentiles. 13 After they finished speaking, James replied, “Brothers, listen to me. 14 Simeon has related how God first visited the Gentiles, to take from them a people for his name. 15 And with this the words of the prophets agree, just as it is written, 16 “‘After this I will return, and I will rebuild the tent of David that has fallen; I will rebuild its ruins, and I will restore it, 17 that the remnant  of mankind may seek the Lord, and all the Gentiles who are called by my name, says the Lord, who makes these things 18 known from of old.’ Acts 15:12-18 (ESV)]
James gets up and quotes Amos to make his point. The gentiles don’t have to become Jews in order to be Christians. He sees the words of Amos being fulfilled in the ministries of Peter and Paul and Barnabas. This is the gospel being fulfilled. So the foundation of the prophets and the apostles is laid, and Jesus is the cornerstone. The three of them have agreed in his name and now it will be accomplished. The gospel is for all people, salvation of all whom God has created even as it is for all of his creation.