One of the most important keys to understanding Scripture is recognizing to whom they are written and to whom they are not. That’s not to say that any part of the Bible is to be avoided; it’s all for us and is profitable (2 Tim. 3:16); it just simply isn’t all to us. As one of the twelve apostles to Israel, John’s writings concerned the fulfillment of prophecy to Israel and were not to churches started by the apostle Paul (cf. Jas. 1:1; 1 Pet. 2:12; 4:3; 3 John 1:7).
The three epistles of John and the other so-called “General Epistles” were written for those who, in the last days (1 John 2:18), will face the Tribulation, which is why they teach a future salvation conditional on faith and works (1 John 2:3; 3:24; Jas. 2:14,24), and why the emphasis is on acknowledging Jesus as the Son of God, instead of believing in the death, burial, and resurrection (cf. 1 John 2:2; 4:2,3,15; 5:13,20). As far as to whom they were given upon completion, we are left to a certain amount of speculation.
In the case of the three epistles of John, he addresses the second to an “elect lady” (2 John 1:1) and the third to a man by the name of Gaius (3 John 1:1), and so we would conclude these letters were given to these individuals apart from any church.
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