Paul is writing to the church at Rome about justification to God. He explained how we can be justified and forgiven of sin through faith in Jesus Christ. Paul used old testament scriptures to prove his point. Remember the bible is one book and not divided. Which includes the Jews and the Gentiles. Paul, in chapter 15 of Romans, says that your faith is for other people. You are to reach out and help the world, not to keep praying for yourself. He also says the God called the gentiles to the faith in Jesus. And we as believers are to go into the world and preach the gospel. So that at least some will be saved. Paul was headed to Jerusalem with a collection for the saints. He was leaving Greece headed home. He told the Roman church he was going to see them soon. Then he prayed for them. Paul wrote about reaching the world for Jesus. And that world is just outside your front door. Helping other and not yourself is the call of God.