Carnal Generation Condemned on Account of Original Sin
He sets forth that this absolute weakness, or rather condemnation, of carnal generation is from the transgression of original sin, when, treating of his own sins, he shows, as it were, their causes, and says that “man that is born of a woman has but a short time to live, and is full of wrath.” Of what wrath, but of that in which all are, as the apostle says, “by nature,” that is, by origin, “children of wrath,” inasmuch as they are children of the concupiscence of the flesh and of the world?
He further shows that to this same wrath also pertains the death of man. For after saying, “He has but a short time to live, and is full of wrath,” he added, “Like a flower that has bloomed, so does he fall; he is gone like a shadow, and continues not.” He then subjoins: “Have You not caused him to enter into judgment with You? For who is pure from uncleanness? Not even one; even should his life last but a day.” In these words he in fact says, You have thrown upon man, short-lived though he be, the care of entering into judgment with You.
For how brief soever be his life—even if it last but a single day—he could not possibly be clean of filth; and therefore with perfect justice must he come under Your judgment. Then, when he says again, “You have numbered all my necessities, and not one of my sins has escaped You: You have sealed up my transgressions in a bag, and hast marked whatever I have done unwillingly;” is it not clear enough that even those sins are justly imputed which are not committed through allurement of pleasure, but for the sake of avoiding some trouble, or pain, or death?
Now these sins, too, are said to be committed under some necessity, whereas they ought all to be overcome by the love and pleasure of righteousness. Again, what he said in the clause, “You have marked whatever I have done unwillingly,” may evidently be connected with the saying: “For what I would, that I do not; but what I hate, that do I.”
Source: Merits and Remission of Sin, and Infant Baptism (New Advent)