Where is this writing that the Apostle wrote to that church? This is still less clear. This Epistle is not among the present Epistles of the Apostle. It is improbable that the First Epistle of this Apostle is meant, especially since there is not the slightest indication in that Epistle about traveling preachers of the Gospel, and especially about Diotrephes.
It is wholly improbable that a writing of the Apostle and Evangelist, and one addressed to an entire church, should have been lost, when even such small and private Epistles as the Second and Third, addressed to private persons, have been preserved. The common consciousness of the Church is opposed to the thought that writings of the God-inspired Apostles could be lost.
The most probable supposition, based also on certain ancient manuscripts, including Tischendorf's Sinaitic Codex, is that one should read not "I wrote to the church," but "I would have written to the church." This also agrees with the context of the discourse.
The meaning is this: concerning these strangers, I would have written not only to you, and not merely a little, but to your whole church, or Christian community, in which you live. But Diotrephes might have abused this letter. It is better that when I myself come to you (3 Jn 1:14), I will personally arrange this matter and do what is necessary with Diotrephes himself.
"Diotrephes, who loves to have the preeminence": who this Diotrephes was, why he loved preeminence, why such preeminence was entrusted to him, and on what his claims to preeminence were based, are not precisely known. It is clear only that he was proud, ambitious, power-loving, and self-willed.
"Does not receive us": that is, even the Apostle himself, and the apostolic disciples, believers, and traveling preachers of the Gospel. It is improbable that Diotrephes did not receive and did not wish to receive even the Apostle personally. Probably, by "us" the Apostle means chiefly the traveling preachers. In humility and abundant love he only places himself alongside them.
Further, the Apostle threatens to stop his disorder with a strict and authoritative word. He would probably punish him by the authority given to him, to which no Diotrephes could fail to submit under danger of excommunication from the Church, that is, anathema. The Apostle Paul sometimes acted in this way (1 Cor 5:5; 1 Tim 1:20).