I wrote to the church, but Diotrephes, who loves to have the preeminence among them, does not receive us. Therefore, if I come, I will call to mind his deeds which he does, prating against us with malicious words. And not content with that, he himself does not receive the brethren, and forbids those who wish to do so, putting them out of the church. III John 9-10.
In his book of 1,502 stories and illustrations (The Tale of the Tardy Oxcart), Chuck Swindoll has this:
A. T. Robertson, a fine, reliable Baptist scholar of years ago, taught for many years at the Southern Baptist Theological Seminary in Louisville. When he began to write on books of the Bible, he chose on one occasion the Book of 3 John, which talks about Diotrephes. Diotrephes was a man who became a self-appointed boss of a church. And over a period of time, he was the one that excommunicated certain people and he screened whatever was done in the church. As the self-appointed leader, he wouldn’t even let John come to speak as a representative of Christ. So, John wrote a letter and reproved him.