The apostle Peter had warned of false teachers who would arise from within the congregation, bringing in destructive sects. (2Pe 2:1-3) Additionally, Paul had told the overseers of the congregation in Ephesus (where John’s letters were later written) that “oppressive wolves” would enter in, not treating the flock with tenderness. (Ac 20:29, 30) He foretold the great apostasy with its “man of lawlessness.” (2Th 2:3-12) In 98 C.E. it was, therefore, as John said: “Young children, it is the last hour, and, just as you have heard that antichrist is coming, even now there have come to be many antichrists; from which fact we gain the knowledge that it is the last hour.” (1Jo 2:18) Consequently, the letter was most timely and of vital importance for the strengthening of the faithful Christians as a bulwark against the apostasy.

Regarding the antichrist, he spoke very plainly. He said: “These things I write you about those who are trying to mislead you.” (1Jo 2:26) These men were denying that Jesus Christ was the Son of God that had come in the flesh. He explained that they were once with the congregation but had gone out in order that it might be shown that they were not of “our sort.” (2:19) They were not the loyal, loving sort that “have faith to the preserving alive of the soul” but were the sort “that shrink back to destruction.”​—Heb 10:39.