Albert Barnes Commentary 1 John 2:19

"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 they all are not of us." — 1 John 2:19 (ASV)

They went out from us. From the church. That is, they had once been professed followers of the Savior, 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 understand 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 Barnes on Matthew 7:23).

This passage proves that these persons, whatever their pretensions and professions may have been, were never sincere Christians. The same remark may be made of all who apostatize from the faith and become teachers of error. They never were truly converted; never belonged really to the spiritual church of Christ.

For if they had been of us. If they had been sincere and true Christians.

They would no doubt have continued with us. The words "no doubt" are supplied by our translators, but the affirmation is equally strong without them: "they would have remained with us." This affirms, without any ambiguity or qualification, that if they had been true Christians they would have remained in the church; that is, they would not have apostatized.

There could not be a more positive affirmation than that which is implied here: that those who are true Christians will continue to be such, or that the saints will not fall away from grace. John affirms of these persons that if they had been true Christians, they would never have departed from the church. He makes the declaration so general that it may be regarded as a universal truth: that if any are truly of us (that is, if they are true Christians), they will continue in the church, or will never fall away.

The statement is also made to teach that if any do fall away from the church, the fact is full proof that they never had any religion; for if they had been, they would have remained steadfast in the church. But they went out, that they might be made manifest that they were not all of us. It was allowed or permitted in the providence of God that this should occur, so that it might be seen and known that they were not true Christians, or so that their real character might be developed. It was desirable that this should be done for several reasons:

1. So that the church might be purified from their influence (see also Barnes).
2. So that it might not be responsible for their conduct, or reproached on account of it.
3. So that their real character might be developed, and they might themselves see that they were not true Christians.
4. So that, being seen and known as apostates, their opinions and conduct might have less influence than if they were connected with the church.
5. So that they might themselves understand their own true character, and no longer live under the delusive opinion that they were Christians and were safe, but that, seeing themselves in their true light, they might be brought to repentance. For there is only a most slender prospect that any who are deceived in the church will ever be brought to true repentance there; and though the hope is slight that one who apostatizes will repent, such an event is much more probable than it would be if he remained in the church.

Men are more likely to be converted when their character is known and understood than when they are playing a game of deception or are themselves deceived. What is affirmed here of these persons often occurs now; and those who have no true religion are often allowed to apostatize from their profession for the same purposes.

It is better that they should cease to have any connection with the church than that they should remain in it. God often allows them to fall away even from the profession of religion, so that they may not do injury as professing Christians.

This very important passage, then, teaches the following things:

1. When men apostatize from the profession of religion, and embrace fatal error, or live in sin, it proves that they never had any true piety.
2. The fact that such persons fall away cannot be used to prove that Christians ever fall from grace, for it demonstrates nothing on that point, but proves only that these persons never had any real piety. They may have had much that seemed to be religion; they may have been zealous, and apparently devoted to God, and may even have had much comfort and peace in what they took to be piety; they may have been eminently "gifted" in prayer, or may have even been successful preachers of the gospel, but all this does not prove that they ever had any piety, nor does the fact that such persons apostatize from their profession throw any light on a question quite foreign to this—whether true Christians ever fall from grace. .
3. This passage proves that if any are true Christians they will remain in the church, or will certainly persevere and be saved. They may indeed backslide grievously; they may wander far away, pain the hearts of fellow believers, and provide an opportunity for the enemies of religion to speak reproachfully; but the apostle says, if they had been of us, they would have continued with us.
4. One of the best evidences of true piety is found in the fact of continuing with the church. I do not mean nominally and formally, but really and spiritually, having the heart with the church; loving its peace and promoting its welfare; identifying ourselves with real Christians, and showing that we are ready to cooperate with those who love the Lord Jesus and his cause.
5. The main reason why professing Christians are allowed to apostatize is to show that they had no true religion. It is desirable that they should see it themselves; desirable that others should see it also. It is better that it should be known that they had no true religion than that they should remain in the church to be a burden on its work, and a reproach to the cause. By being allowed thus to separate themselves from the church, they may be brought to remember their violated vows, and the church will be free from the reproach of having those in its midst who are a dishonor to the Christian name. We are not to wonder, then, if persons apostatize who have been professors of true religion; and we are not to suppose that the greatest injury is done to the cause when they do it. A greater injury by far is done when such persons remain in the church.