Reading through the second letter of Saint John

This is a really short one. Really short. It has one message: cling to the true faith, there will be false prophets and you will know them when they deny that Christ came in human flesh, this is the spirit of anti-Christ, stay clear of it or lose your heavenly reward. 

And there it is. Saint John identifies himself as an elder of a church that is not specified, and he is addressing another church, possibly as the last surviving Apostle. All the others had been martyred. He addresses this second church as a lady:

"I, the presbyter, send greeting to that sovereign lady whom God has chosen; and to those children of hers who are my friends in the truth, loved, not by me only, but by all those who have recognized the truth." - II John 1

The warning about the anti-Christ is as simple as my summary above. Many Christians think that there is a single figure called anti-Christ who will arrive at a particular moment and cause significant damage to the Church. But it seems to me that John is speaking of a spirit of anti-Christ, a rival religious or political movement that specifically denies that the second person of the most blessed Trinity was incarnated as a human being, in order to bring about our salvation:

"Many false teachers have appeared in the world, who will not acknowledge that Jesus Christ has come in human flesh; here is the deceiver you were warned against, here is Antichrist. Be on your guard, or you will lose all you have earned, instead of receiving your wages in full. The man who goes back, who is not true to Christ’s teaching, loses hold of God; the man who is true to that teaching, keeps hold both of the Father and of the Son. - II John 7-9

Whereas John repeats the teaching that has made his Gospel famous - that we must love Christ by keeping his commandments - his last solemn warning is that we not even entertain the preachers and teachers who bring with them the above anti-Christian idea. We know of historical persons who have presented this idea, and we may know people today who do. John would call them anti-Christ, and that is terrible. We could compare his warning to those made by Saint Paul to his churches to remain in the traditions he had given them and not attempt to go beyond them, such as this one:

"Stand firm, then, brethren, and hold by the traditions you have learned, in word or in writing, from us." - II Thessalonians 2: 14