Proverbs 20:9

Who can say, I have made my heart clean
The heart of than is naturally unclean, the mind, conscience, understanding, will, and affections; there is no part clean, all are defiled with sin; and though there is such a thing as a pure or clean heart, yet not as made so by men; it is God that has made the heart, that can only make it clean, or create a clean heart in men; it is not to be done by themselves, or by anything that they can do; it is done only by the grace of God, and blood of Christ: God has promised to do it, and he does it; and to him, and to him only, is it to be ascribed; I am pure from my sin?
the sin of nature or of action: such indeed who are washed from their sins in the blood of Christ; whose sins are all pardoned for his sake, and who are justified from all things by his righteousness; they are pure from sin, none is to be seen in them, or found upon them in a legal sense: they are all fair and comely, and without fault in the sight of God; their iniquities are caused to pass from them; and they are clothed with fine linen, clean and white, the righteousness of the saints: but then none are pure from indwelling sin, nor from the commission of sin; no man can say this, any more than the former; if he does, he is an ignorant man, and does not know the plague of his heart; and he is a vain pharisaical man; yea, a man that does not speak the truth, nor is the truth in him, ( 1 John 1:8 ) .