Gregory the Dialogist

The light shall be dark in his tabernacle. If we very frequently take darkness for sorrow, we ought without unfairness to take light for joy. And so 'the light is dark in his tabernacle,' in that in his conscience, which he inhabits in wickedness, the joy which he had from things temporal is brought to an end. Whence too it is fitly added; And the candle that is over him shall be put out. …

Morals on the Book of Job, Book XIV ↗

Thomas Aquinas

We should note that the prosperity of man's success comes from two causes. Sometimes it comes from human providence, for example, when a man prudently and carefully orders each and every thing. As to this cause he says of the end of this prosperity, "The light will grow dark in the tent of that man?" because both he and his household will lack prudence in their decisions. Sometimes however, the prosperity of a man's success comes from a higher cause, from divine providence. …

Commentary on Job ↗