Gregory the Dialogist

Ver. 12. They have changed the night into day. For 'the thoughts being scattered change night into day,' in that it is sometimes more grateful to the righteous through adversity to undergo sufferings, rather than as the effect of prosperity to be harassed with the charge of earthly ministering. But because they have learnt by paying attention that both adversity passes away, and prosperity dawns again, it is fitly added; And again after darkness I look for light. …

Morals on the Book of Job, Book XIII ↗

Thomas Aquinas

This torture of the heart was not even interrupted by night which is the time set aside for man's rest, and so he then says, "They have turned night into day," because of the reflection previously mentioned he spent the night in insomnia as though it were day. It is more painful to suffer the loss of sleep at night than during the day, because during the day the soul of man is lightened by the company of men and by the sight of daylight. So as long as night was sleepless for him he desired that it end quickly. …

Commentary on Job ↗