1 John 1:8

If we say that we have no sin
Notwithstanding believers are cleansed from their sins by the blood of Christ, yet they are not without sin; no man is without sin: this is not only true of all men, as they come into the world, being conceived in sin, and shapen in iniquity, and of all that are in a state of unregeneracy, and of God's elect, while in such a state, but even of all regenerated and sanctified persons in this life; as appears by the ingenuous confessions of sin made by the saints in all ages; by their complaints concerning it, and groans under it; by the continual war in them between flesh and spirit; and by their prayers for the discoveries of pardoning grace, and for the fresh application of Christ's blood for cleansing; by their remissness in the discharge of duty, and by their frequent slips and falls, and often backslidings: and though their sins are all pardoned, and they are justified from all things by the righteousness of Christ, yet they are not without sin; though they are freed from the guilt of sin, and are under no obligation to punishment on account of it, yet not from the being of it; their sins were indeed transferred from them to Christ, and he has bore them, and took them and put them away, and they are redeemed from them, and are acquitted, discharged, and pardoned, so that sin is not imputed to them, and God sees no iniquity in them in the article of justification; and also, their iniquities are caused to pass from them, as to the guilt of them, and are taken out of their sight, and they have no more conscience of them, having their hearts sprinkled and purged by the blood of Jesus, and are clear of all condemnation, the curse of the law, the wrath of God, or the second death, by reason of them; yet pardon of sin, and justification from it, though they take away the guilt of sin, and free from obligation to punishment, yet they do not take out the being of sin, or cause it to cease to act, or do not make sins cease to be sins, or change the nature of actions, of sinful ones, to make them harmless, innocent, or indifferent; the sins of believers are equally sins with other persons, are of the same kind and nature, and equally transgressions of the law, and many of them are attended with more aggravating circumstances, and are taken notice of by God, and resented by him, and for which he chastises his people in love: now though a believer may say that he has not this or that particular sin, or is not guilty of this or that sin, for he has the seeds of all sin in him, yet he cannot say he has no sin; and though he may truly say he shall have no sin, for in the other state the being and principle of sin will be removed, and the saints will be perfectly holy in themselves, yet he cannot, in this present life, say that he is without it: if any of us who profess to be cleansed from sin by the blood of Christ should affirm this,

we deceive ourselves;
such persons must be ignorant of themselves, and put a cheat upon themselves, thinking themselves to be something when they are nothing; flattering themselves what pure and holy creatures they are, when there is a fountain of sin and wickedness in them; these are self-deceptions, sad delusions, and gross impositions upon themselves:

and the truth is not in us;
it is a plain case the truth of grace is not in such persons, for if there was a real work of God upon their souls, they would know and discern the plague of their own hearts, the impurity of their nature, and the imperfection of their obedience; nor is the word of truth in them, for if that had an entrance into them, and worked effectually in them, they would in the light of it discover much sin and iniquity in them; and indeed there is no principle of truth, no veracity in them; there is no sincerity nor ingenuity in them; they do not speak honestly and uprightly, but contrary to the dictates of their own conscience.