John Chrysostom
What then does "that your rejoicing may abound" mean? It means that what serves for praise should abound, namely confirmation in faith, which is praise in Christ, and righteous life. Is it then in me, "that your rejoicing may abound by my coming to you again"? Yes, he says. "For what is our hope, or joy, or crown of rejoicing? Is it not even you?" (1 Thess 2:19). "As also you are our boast, even as we also are yours" (2 Cor 1:14). That is, so that I may have more to boast of in you. How so? "That your rejoicing may abound." I can boast more when you make progress. "By my coming to you again." What then? Did he come to them? Search out for yourselves whether he came.