Paul didn’t think small. He certainly wasn’t concerned with the fact that he believed the Truth about Jesus Christ was for all people. I think it is much easier to have a small faith, sorry not the kind that Jesus says moves mountains, I mean a faith that is about you and your relationship with God and your problems and worries. It’s a faith that prays about my stuff, a faith that trusts God for everything concerning me. That’s a small faith and it stays small because it factors in only one human and one God.
Paul’s words don’t reflect that kind of faith, he says in Ephesians 3:5-6
the mystery of Christ, which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit. This mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel.
First of all the message Paul has to share is not just for himself, his family or his friends, it’s for the whole world. The Jewish people had two big categories for humankind – Jews and Gentiles. Paul is saying that now God’s promise pushes through any previous perceived boundaries into both those categories, all the world. Paul probably didn’t even have a concept of how big that was but his faith, powered by the Holy Spirit, had no problem in doing math on that scale.
Secondly Paul’s faith seems to get small for a second in verses 7 and 8:
Of this gospel I was made a minister according to the gift of God’s grace, which was given me by the working of his power. To me, though I am the very least of all the saints, this grace was given, to preach to the Gentiles the unsearchable riches of Christ.
Paul focuses in on the gift of faith that was given to him. A personal faith that Paul recognizes as a gift created through the working of God’s power. Paul’s faith gets small only in the sense that he talks about his personal faith in God, Paul doesn’t go passed that recollection into the realm of personal needs, his faith has a purpose, to share that Gospel with those who have not heard it. That’s big faith.