From the early Church Fathers to now.
“Who can say: My heart is clean, I am pure from sin?”
“Whose soul, then, is pure from stain? How has anyone not been struck by vanity or been trodden down by the foot of pride? Whose hand has never been touched by sin? Whose feet have never run toward evil? Who has not been polluted by a roving eye or been defiled by an undisciplined ear? Whose taste has never been preoccupied by its enjoyment, whose heart has remained unmoved by vain emotions?”
“Let us not therefore give up in despair; for to fall is not so grievous as to lie where we have fallen. It is not so dreadful to be wounded as it is to refuse healing after being wounded. "For who shall boast that he has his heart chaste? or who shall say confidently that he is pure from sin?" These things I say not to make you more negligent but to prevent your despairing.”
“"Who can say," writes the wise man, "I have made my heart clean"? The stars are not pure in the Lord's sight; how much less people whose whole life is one long temptation.”
“The merciful God has provided for the inhabitants of earth repentance as the medicine of salvation. Some endeavor to dispense with repentance, saying of themselves that they are clean. In their great madness they do not understand that to entertain such an idea of themselves is full of all impurity. For "no man is free from defilement," as it is written.”
“Who can say, My heart is clean, I am pure from sin? It should be noted that He does not say, Who can have a clean heart and be pure from sin? But He says, Who can say, My heart is clean, I am pure from sin? Because there are those who, by the grace of God, can have according to human measure the purity of heart and work. Hence the Lord's saying, Blessed are the clean of heart, for they shall see God (Matthew 5); and in the psalm: Who shall ascend into the mountain of the Lord, or who shall stand in His holy place? He that has clean hands and a pure heart (Psalm 23). For if no one has a clean heart, and there is none pure from sin, it would certainly follow that no one would ascend the mountain of the Lord, nor would any man stand in His holy place. But because it is certain that many will ascend the mountain of the Lord, and will stand in His holy place, therefore many must have a clean heart, and according to the measure of human possibility, be pure from sin. Yet no one should rashly declare himself clean of heart and free from sin. For the boasting of one's own praise is foolish; it is rash to glory in one's own innocence or justice. And because there are those who tend to praise their own deeds as excellent and criticize the deeds of others as vile, it is rightly added:”
“No human, therefore, is without sin. Labor therefore to the utmost of your power to be unblamable; and be solicitous of all the parts of your flock, lest any one be scandalized on your account and thereby perish.”
The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.