Job 3:4

According to Job's words, he desires that the moon or the stars might not illuminate his night but that it may be obscured by thick darkness, which Job calls the shadow of death. If one carefully examines the text's meaning, Job demands through his prayers …

Learn here the reason which led the Emmanuel to a new birth in the flesh. Certainly the sin of the world was the reason for the advent of Christ.

HISTORICAL INTERPRETATION. Let that day be turned into darkness. This day shines as it were in the hearts of men, when the persuasions of his wickedness are thought to be for our good, and what they are within is never seen; but when his wickedness is seen as it is, the day of false promises is as it were dimmed by a kind of darkness spread before the eyes of our judgment, in this respect, that such as he is in intrinsic worth, such he is perceived to be in his beguilement, and so 'the day becomes darkness,' when we take as adverse even the very things, which he holds out as advantageous whilst persuading them. 'The day becomes darkness,' when our old enemy, even when lurking under the cloak of his blandishments, is perceived by us to be such as he is when ravening after us, that he may never mock us with feigned prosperity, as though by the light of day, dragging us by real misery to the darkness of sin. Let not God regard it from above, neither let the light shine upon it. As Almighty God was able to create good things out of nothing, so, when He would, He also restored the good things that were lost, by the mystery of His Incarnation. Now he had made two creations to contemplate Himself, viz. the Angelic and the human, but Pride smote both, and dashed them from the erect station of native uprightness. But one had the clothing of the flesh, the other bore no infirmity derived from the flesh. For an angelical being is spirit alone, but man is both spirit and flesh. Therefore when the Creator took compassion to work redemption, it was meet that He should bring back to Himself that creature, which, in the commission of sin, plainly had something of infirmity; and it was also meet that the apostate Angel should be driven down to a farther depth, in proportion as he, when he fell from resoluteness in standing fast, carried about him no infirmity of the flesh. […]

MORAL INTERPRETATION. Let that day be darkness. For 'the day becomes darkness,' when in the very commencement of the enjoyment, we see to what an end of ruin sin is hurrying us. We 'turn the day into darkness,' whenever by severely chastising ourselves, we turn to bitter the very sweets of evil enjoyment by the keen laments of penance, and, when we visit it with weeping, whereinsoever we sin in gratification in our secret hearts.

After cursing the day of his birth and the night of his conception, one by one the curse for each of these periods of time. First with the curse of the day of his birth, "Let that day be darkness!" Consider that, as Jerome says …