If we deny that we have sinned, we make Him a liar, and His Message has no place in our hearts.

If we say that we have no sin, we make him false and his word is not in us.

If we claim that we have not sinned, then we make him a liar, and his Word is not in us.

We make him a liar He goes still further, that they who claim purity for themselves blaspheme God. For we see that he everywhere represents the whole race of man as guilty of sin. Whosoever then tries to escape this charge carries on war with God, and accuses him of falsehood, as though he condemned the undeserving. To confirm this he adds, and his word is not in us; as though he had said, that we reject this great truth, that all are under guilt. We hence learn, that we then only make a due progress in the knowledge of the word of the Lord, when we become really humbled, so as to groan under the burden of our sins and learn to flee to the mercy of God, and acquiesce in nothing else but in his paternal favor.

If we say that we have not sinned - In times that are past. Some perhaps might be disposed to say this; and as the apostle is careful to guard every point, he here states that if a man should take the ground that his past life had been wholly upright, it would prove that he had no true religion. The statement here respecting the past seems to prove that when, in 1-John 1:8, he refers to the present - "if we say we have no sin" - he meant to say that if a man should claim to be perfect, or to be wholly sanctified, it would demonstrate that he deceived himself; and the two statements go to prove that neither in reference to the past nor the present can anyone lay claim to perfection.
We make him a liar - Because he has everywhere affirmed the depravity of all the race. Compare the notes at Romans. 1; 2; 3. On no point have his declarations been more positive and uniform than on the fact of the universal sinfulness of man. Compare Genesis 6:11-12; Job 14:4; Job 15:16; Psalm 14:1-3; Psalm 51:5; Psalm 58:3; Romans 3:9-20; Galatians 3:21.
And his word is not in us - His truth; that is, we have no true religion. The whole system of Christianity is based on the fact that man is a fallen being, and needs a Saviour; and unless a man admits that, of course he cannot be a Christian.
Remarks On 1-John 1
(1) The importance of the doctrine of the incarnation of the Son of God, 1-John 1:1-2. On that doctrine the apostle lays great stress; begins his Epistle with it; presents it in a great variety of forms; dwells upon it as if he would not have it forgotten or misunderstood. It has all the importance which he attached to it, for.
(a) it is the most wonderful of all the events of which we have any knowledge;
(b) it is the most deeply connected with our welfare.
(2) the intense interest which true piety always takes in this doctrine, 1-John 1:1-2. The feelings of John on the subject are substantially the feelings of all true Christians. The world passes it by in unbelief, or as if it were of no importance; but no true Christian can look at the fact that the Son of God became incarnate but with the deepest emotion.
(3) it is an object of ardent desire with true Christians that all others should share their joys, 1-John 1:3-4. There is nothing selfish, or narrow, or exclusive in true religion; but every sincere Christian who is happy desires that all others should be happy too.
(4) wherever there is true fellowship with God, there is with all true Christians, 1-John 1:3-4. There is but one church, one family of God; and as all true Christians have fellowship with God, they must have with each other.
(5) wherever there is true fellowship with Christians, there is with God himself, 1-John 1:3-4. If we love his people, share their joys, labor with them in promoting his cause, and love the things which they love, we shall show that we love him. There is but one God, and one church; and if all the members love each other, they will love their common God and Saviour. An evidence, therefore, that we love Christians, becomes an evidence that we love God.
(6) it is a great privilege to be a Christian, 1-John 1:3-4. If we are Christians, we are associated with:
(a) God the Father;
(b) with his Son Jesus Christ;
(c) with all his redeemed on earth and in heaven;
(d) with all holy angels.
There is one bond of fellowship that unites all together; and what a privilege it is to be united in the eternal bonds of friendship with all the holy minds in the universe!
(7) if God is "light" 1-John 1:5, then all that occurs is reconcilable with the idea that he is worthy of confidence. What he does may seem to be dark to us, but we may be assured that it is all light with him. A cloud may come between us and the sun, but beyond the cloud the sun shines with undimmed splendor, and soon the cloud itself will pass away. At midnight it is dark to us, but it is not because the sun is shorn of his beams, or is extinguished. He will rise again upon our hemisphere in the fullness of his glory, and all the darkness of the cloud and of midnight is reconcilable with the idea that the sun is a bright orb, and that in him is no darkness at all. So with God. We may be under a cloud of sorrow and of trouble, but above that the glory of God shines with splendor, and soon that cloud will pass away, and reveal him in the fullness of his beauty and truth.
(8) we should, therefore, at all times exercise a cheerful confidence in God, 1-John 1:5. Who supposes that the sun is never again to shine when the cloud passes over it, or when the shades of midnight have settled down upon the world? We confide in that sun that it will shine again when the cloud has passed off, and when the shades of night have been driven away. So let us confide in God, for with more absolute certainty we shall yet see him to be light, and shall come to a world where there is no cloud.
(9) we may look cheerfully onward to heaven, 1-John 1:5. There all is light. There we shall see God as He is. Well may we then bear with our darkness a little longer, for soon we shall be ushered into a world where there is no need of the sun or the stars; where there is no darkness, no night.
(10) Religion is elevating in its nature, 1-John 1:6-7. It brings us from a world of darkness to a world of light. It scatters the rays of light on a thousand dark subjects, and gives promise that all that is now obscure will yet become clear as noonday. Wherever there is true religion, the mind emerges more and more into light; the scales of ignorance and error pass away.
(11) there is no sin so great that it may not be removed by the blood of the atonement, 1-John 1:7, "last clause." This blood has shown its efficacy in the pardon of all the great sinners who have applied to it, and its efficacy is as great now as it was when it was applied to the first sinner that was saved. No one, therefore, however great his sins, needs to hesitate about applying to the blood of the cross, or fear that his sins are so great that they cannot be taken away!
(12) the Christian will yet be made wholly pure, 1-John 1:7, "last clause." It is of the nature of that blood which the Redeemer shed that it ultimately cleanses the soul entirely from sin. The prospect before the true Christian that he will become perfectly holy is absolute; and whatever else may befall him, he is sure that he will yet be holy as God is holy.
(13) there is no use in attempting to conceal our offences, 1-John 1:8. They are known, all known, to one Being, and they will at some future period all be disclosed. We cannot hope to evade punishment by hiding them; we cannot hope for impunity because we suppose they may be passed over as if unobserved. No man can escape on the presumption either that his sins are unknown, or that they are unworthy of notice.
(14) it is manly to make confession when we have sinned, 1-John 1:9-10. All meanness was in doing the wrong, not in confessing it; what we should be ashamed of is that we are guilty, not that confession is to be made. When a wrong has been done, there is no nobleness in trying to conceal it; and as there is no nobleness in such an attempt, so there could be no safety.
(15) peace of mind, when wrong has been done, can be found only in confession, 1-John 1:9-10. That is what nature prompts to when we have done wrong, if we would find peace, and that the religion of grace demands. When a man has done wrong, the least that he can do is to make confession; and when that is done and the wrong is pardoned, all is done that can be to restore peace to the soul.
(16) the "ease" of salvation, 1-John 1:9. What more easy terms of salvation could we desire than an acknowledgment of our sins? No painful sacrifice is demanded; no penance, pilgrimage, or voluntary scourging; all that is required is that there should be an acknowledgment of sin at the foot of the cross, and if this is done with a true heart the offender will be saved. If a man is not willing to do this, why should he be saved? How can he be?

(7) If we say that we have not sinned, we make him (i) a liar, and his (k) word is not in us.
(7) A repeat of the former verse, in which he condemned all of sin without exception: so much so that if any man persuade himself otherwise, he does as much as in him lies, make the word of God himself useless and to no effect, yes, he makes God a liar: for to why in times past did we need sacrifices, or now Christ and the gospel, if we are not sinners?
(i) They do not only deceive themselves but are blasphemous against God.
(k) His doctrine shall have no place in us; that is, in our hearts.

If we say that we have not sinned,.... Have never sinned, in time past as well as now; deny original sin, and that men are born in sin, but affirm they come into the world pure and holy; and assert that concupiscence is not sin; and so not regarding internal lusts and desires as sinful, only what is external, fancy they have so lived as to have been without sin: but if any of us give out such an assertion,
we make him a liar: that is, God, who in his word declares that the wicked are estranged from the womb, and go astray as soon as they be born, speaking lies; that his own people are transgressors from the womb; that all have sinned and come short of his glory; and that there is none that does good, no, not one, but all are under sin, under the power and guilt of it, and become filthy by it, and so obnoxious to the wrath of God:
and his word is not in us; either Christ the Word of God, or rather the word of God which declares these things; no regard is had unto it; it "is not with us", as the Syriac and Ethiopic versions render it; it is not used and attended to as the rule and standard of truth, but is east away and despised; at least it has no place in the hearts of such, nor does it work effectually; for, was this the case, they would have other notions of themselves than that of sinless creatures. The apostle has regard either to the Gnostics, a set of heretics of this age, who fancied themselves pure, spiritual, and perfect, even in the midst of all their impurities, and notwithstanding their vicious lives; or to judaizing Christians, and it may be to the Jews themselves, who entertained such sort of notions as these of being perfect and without sin (h).
(h) Vid. T. Bab. Temura, fol. 15. 2. & Bava Kama, fol. 80. 1. T. Hieros. Sota, fol. 24. 1. &. Chagiga, fol. 77. 4.

Parallel to 1-John 1:8.
we have not sinned--referring to the commission of actual sins, even after regeneration and conversion; whereas in 1-John 1:8, "we have no sin," refers to the present GUILT remaining (until cleansed) from the actual sins committed, and to the SIN of our corrupt old nature still adhering to us. The perfect "have . . . sinned" brings down the commission of sins to the present time, not merely sins committed before, but since, conversion.
we make him a liar--a gradation; 1-John 1:6, "we lie"; 1-John 1:8, "we deceive ourselves"; worst of all, "we make Him a liar," by denying His word that all men are sinners (compare 1-John 5:10).
his word is not in us--"His word," which is "the truth" (1-John 1:8), accuses us truly; by denying it we drive it from our hearts (compare John 5:38). Our rejection of "His word" in respect to our being sinners, implies as the consequence our rejection of His word and will revealed in the law and Gospel as a whole; for these throughout rest on the fact that we have sinned, and have sin.

Yet still we are to retain, even to our lives' end, a deep sense of our past sins. Still if we say, we have not sinned, we make him a liar - Who saith, all have sinned. And his word is not in us - We do not receive it; we give it no place in our hearts.