In I John it is a question of apostasy, in Jude of corruption. In John the antichrists go out; in Jude the false brethren come in, and with them corruption. In Jude those who separate are like the Pharisees who took the first places. The ungodly are still seen in the midst of the faithful (Jude 44For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ. (Jude 4),15).
Cain, Balaam and Korah are the three characters of the evil within. In John it is apostasy; they go out. Such is the character of these antichrists. They deny that Jesus is the Christ; it is Wish unbelief They deny too the Father told the Son; it is unbelief as to Christian truth. The evil of John and that of Jude, antichristianism and corruption, can coexist, just as we may see it in prophecy.