1 John 2:18-19

¹⁸ Little children, it is the last hour; and as you have heard that the Antichrist is coming, even now many antichrists have come, by which we know that it is the last hour.

¹⁹ They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.

last hour (v.18) — Only one last hour was in view, namely the closing period previous to the return of the Lord Jesus. There is a connection of thought between this statement and that of the preceding verse, that “the world passeth away and the lust thereof.” “Hour” suggests the brevity and the critical character of the time. — Vine, pages 35-36.

__________

The term “antichrist” (v.18) is used in the New Testament only by John, and only in this and the next Epistle; it signifies not only one who takes the place of Christ, but one who is antagonistic to Him. The Antichrist will both seek to usurp the authority of Christ and oppose Him, as did the already existent antichrists by their false teachings (v.22), cp. 2 Thessalonians 2:3. — Vine, page 36.

__________

[The antichrists] had evidently sought to identify themselves with the saints. They were not actually united to Christ as real members o His body; professing identification with the saints they partook of their spiritual privileges, but in reality they were traitors to the truth, as their false teachings showed. — Vine, page 36. 

__________

The Apostle is not teaching here that a Christian cannot fall away and backslide. That is not the subject with which he is now dealing. He is making clear the distinction between the genuine and the false in matters of doctrine, as he does in the next chapter in regard to matters of practice. — Vine, page 37.