1 Thessalonians 3:4

For even when we were with you, we warned you plainly in advance that we were going to experience persecution; and so, as you know, it has come to pass.  

Paul endured great persecution and still kept the faith. God was able to work through Paul and bring many to the faith because Paul didn’t give up or doubt. Paul had many experiences that only God could get him through, and because of that, Paul never gave up his faith. God will do the same for us as we keep our faith in Him.