1 John 1:8

If we say that we have no sin - It is not improbable that the apostle here makes allusion to some error which was then beginning to prevail in the church. Some have supposed that the allusion is to the sect of the Nicolaitanes, and to the views which they maintained, particularly that nothing was forbidden to the children of God under the gospel, and that in the freedom conferred on Christians they were at liberty to do what they pleased, Revelation 2:6, Revelation 2:15. It is not certain, however, that the allusion is to them, and it is not necessary to suppose that there is reference to any particular sect that existed at that time. The object of the apostle is to show that it is implied in the very nature of the gospel that we are sinners, and that if, on any pretence, we denied that fact, we utterly deceived ourselves. In all ages there have been those who have attempted, on some pretence, to justify their conduct; who have felt that they did not need a Saviour; who have maintained that they had a right to do what they pleased; or who, on pretence of being perfectly sanctified, have held that they live without the commission of sin. To meet these, and all similar cases, the apostle affirms that it is a great elementary truth, which on no pretence is to be denied, that we are all sinners. We are at all times, and in all circumstances, to admit the painful and humiliating truth that we are transgressors of the law of God, and that we need, even in our best services, the cleansing of the blood of Jesus Christ. The fair interpretation of the declaration here will apply not only to those who maintain that they have not been guilty of sin in the past, but also to those who profess to have become perfectly sanctified, and to live without sin. In any and every way, if we say that we have no sin, we deceive ourselves. Compare the notes at James 3:2.

We deceive ourselves - We have wrong views about our character. This does not mean that the self-deception is willful, but that it in fact exists. No man knows himself who supposes that in all respects he is perfectly pure.

And the truth is not in us - On this subject. A man who should maintain that he had never committed sin, could have no just views of the truth in regard to himself, and would show that he was in utter error. In like manner, according to the obvious interpretation of this passage, he who maintains that he is wholly sanctified, and lives without any sin, shows that he is deceived in regard to himself, and that the truth, in this respect, is not in him. He may hold the truth on other subjects, but he does not on this. The very nature of the Christian religion supposes that we feel ourselves to be sinners, and that we should be ever ready to acknowledge it. A man who claims that he is absolutely perfect, that he is holy as God is holy, must know little of his own heart. Who, after all his reasoning on the subject, would dare to go out under the open heaven, at midnight, and lift up his hands and his eyes toward the stars, and say that he had no sin to confess - that he was as pure as the God that made those stars?