Why did Paul use the word “Gentiles” in Romans 11:25 when it is the Church he was referring to that would come into “fullness”? Shouldn’t it be “fullness of believers” since the Church consists of both Jews and Gentiles?
Yes, the Church consists of those who were formerly Jews and those who were formerly Gentiles. Paul explained this in Ephesians 2:14-16. I believe Paul used the word Gentiles in Romans 11:25 to be consistent with what he heard James say in Acts 15:13-18 to the effect that Israel was being set aside while the Lord takes a people for Himself from among the Gentiles. James was also referring to the Church.