1 John 2:19

Those who were opposing Christ had gone out from "us." "Us" may mean the apostolic eyewitnesses, as often elsewhere in this epistle (cf. 1 John 1:1-5; 1 John 4:6). This would mean that these false teachers had gone out from among the apostles, not that they were apostles themselves, claiming that their message was what the apostles endorsed (cf. Acts 15:1; 2 Corinthians 11:5). "Us" elsewhere in this epistle refers to the believing community (cf. 1 John 1:6 to 1 John 2:2), and I think it probably means that here. Some false teachers evidently had been members of local house-churches and then left them because of doctrinal differences. The physical separation of these men from the apostles and the faithful eventually illustrated their doctrinal separation from them.

"From other references to ’antichrists’ in this letter it is evident that when the writer uses this term he means the heterodox ex-members of his own community: those who, in one way or another, were denying the true identity of Jesus, and the fact of God’s saving activity mediated to the world through him." [Note: Smalley, p. 101.]

". . . it is possible, in this instance, that those who later allowed their heretical thought and actions to run away with them (when it could obviously be said, ouk esan ex emon, ’they were not of us’) were in the first place believers with a genuine, if uninformed, faith in Jesus." [Note: Ibid., p. 103. Cf. Hodges, The Epistles . . ., pp. 109-10.]

"If you will investigate the history of the false cults and antichristian religious systems in today’s world, you will find that in most cases their founders started out in a local church! They were ’with us’ but not ’of us,’ so they went out ’from us’ and started their own groups." [Note: Wiersbe, p. 499.]

". . . a person who makes a genuine confession can be expected to persevere in his faith, although elsewhere John warns his readers against the danger of failure to persevere [cf. 1 John 2:24; 2 John 1:8]." [Note: Marshall, p. 152.]

Perseverance in faith and good works is normal for a Christian, but it is not inevitable. Hence we have all the warnings and exhortations to continue in faith and good works in the New Testament.

Whereas divisions within Christendom create obvious problems, God causes some good to come out of them by using these divisions to clarify doctrinal differences and deviations from the truth.