Proverbs 20:9

9 Who can say I have made my heart clean, I am pure from my sins? It is the same thought that Solomon expresses in his prayer at the consecration of the temple, Kg1 8:46 : there is no man who sinneth not. To cleanse his heart (as Psa 73:13), is equivalent to to empty it, by self-examination and earnest effort after holiness, of all impure motives and inclinations; vid., regarding זכה, to be piercing, shining brightly, cloudlessly pure, Fleischer in Levy's Chald. Wrterbuch, i. 424. The consequence of זכּות is, becoming pure; and the consequence of זכּות לב, i.e., of the purifying of the heart, the being pure from sinful conduct: I have become pure from my sins, i.e., from such as I might fall into by not resisting temptations; the suffix is not understood as actual, but as potential, like Psa 18:24. No one can boast of this, for man's knowledge of himself and of his sins remains always limited (Jer 17:9.; Psa 19:13); and sin is so deeply rooted in his nature (Job 14:4; Job 15:14-16), that the remains of a sinful tendency always still conceal themselves in the folds of his heart, sinful thoughts still cross his soul, sinful inclinations still sometimes by their natural force overcome the moral resistance that opposes them, and stains of all kinds still defile even his best actions.

This question is not only a challenge to any man in the world to prove himself sinless, whatever he pretends, but a lamentation of the corruption of mankind, even that which remains in the best. Alas! Who can say, "I am sinless?" Observe, 1. Who the persons are that are excluded from these pretensions - all, one as well as another. Here, in this imperfect state, no person whatsoever can pretend to be without sin. Adam could say so in innocency, and saints can say so in heaven, but none in this life. Those that think themselves as good as they should be cannot, nay, and those that are really good will not, dare not, say this. 2. What the pretension is that is excluded. We cannot say, We have made our hearts clean. Though we can say, through grace, "We are cleaner than we have been," yet we cannot say, "We are clean and pure from all remainders of sin." Or, though we are clean from the gross acts of sin, yet we cannot say, "Our hearts are clean." Or, though we are washed and cleansed, yet we cannot say, "We ourselves made our own hearts clean;" it was the work of the Spirit. Or, though we are pure from the sins of many others, yet we cannot say, "We are pure from our sin, the sin that easily besets us, the body of death which Paul complained of," Rom 7:24.

20:9 Wise people recognize their own weaknesses. Pride prohibits people from seeing their faults (6:17-18; 11:2; 13:10; 15:33; 16:18; 18:12; see also 1 Jn 1:8-10).