1 John 2:19

“They went out from us, &c.] Which intends not the persons that went down from Judea to Antioch, (<441501>Acts 15:1,24), who preached destructive doctrines to the Gentiles, which the apostles and the church of Judea disowned and censured; by which it appeared, that all the preachers of these doctrines were not of them, and of the same mind with them: for this sense makes these antichrists to be only preachers; whereas, though many of them might be such, yet not all; for whoever, in a private capacity denied the Father and the Son, or that Christ was come in the flesh, was antichrist; and to these private believers are opposed in (<620220>1 John 2:20); and it also makes the “us” to be the…”

“out from us--from our Christian communion. Not necessarily a formal secession or going out: thus Rome has spiritually gone out, though formally still of the Christian Church. not of us--by spiritual fellowship (Jo1 1:3). "They are like bad humors in the body of Christ, the Church: when they are vomited out, then the body is relieved; the body of Christ is now still under treatment, and has not yet attained the perfect soundness which it shall have only at the resurrection" [AUGUSTINE, Ten Homilies on the First Epistle of John, Homily 3.4]. they would . . . have continued--implying the indefectibility of grace in the elect. "Where God's call is effectual, there will be sure perseverance"…”

“They went out from us - From the church. That is, they had once been professors of the religion of the Saviour, though their apostasy showed that they never had any true piety. John refers to the fact that they had once been in the church, perhaps to remind those to whom he wrote that they knew them well, and could readily appreciate their character. It was a humiliating statement that those who showed themselves to be so utterly opposed to religion had once been members of the Christian church; but this is a statement which we are often compelled to make. But they were not of us - That is, they did not really belong to us, or were not true Christians. See the notes at Matthew 7:23. This…”

“They were not of us - When they went; their hearts were before departed from God, otherwise, they would have continued with us: but they went out, that they might be made manifest - That is, this was made manifest by their going out. 1 John 2:20”

“2:19 These people left our churches: This is John’s first direct statement about the false teachers. At one point, they had been part of the church community, in fellowship with John and the other apostles. Then they left that fellowship and evidently formed a separate, exclusive community based on their false teachings about Jesus (see 4:1; 2 Jn 1:7; 3 Jn 1:9-10). • they never really belonged with us: True believers would have stayed in fellowship with the apostles and remained faithful to their teachings.”

“went out: Deu 13:13; Psa 41:9; Mat 13:20, Mat 13:21; Mar 4:5, Mar 4:6, Mar 4:16, Mar 4:17; Luk 8:13; Joh 15:2; Act 15:24, Act 20:30; Pe2 2:20, Pe2 2:21; Jde 1:19 for: Job 17:9; Psa 37:28, Psa 125:1, Psa 125:2; Jer 32:38-40; Mat 24:24; Mar 13:22; Joh 4:14, Joh 6:37-39, Joh 10:28-30; Ti2 2:10, Ti2 2:19; Pe1 1:2-5; Jde 1:1 they might: Rom 9:6, Rom 11:5, Rom 11:6; Co1 11:19; Ti2 3:9; Heb 10:39 1 John 2:20”