Gregory the Dialogist

The righteous shall see it and be glad; and the innocent one shall laugh them to scorn. The righteous when they see the unrighteous erring here cannot be glad for the error of persons ruining themselves. For if they rejoice in errings, they cease to be righteous. Again, if in the feeling of triumph they be glad, for this that they are not such as they see others are, they are altogether full of pride. …

Morals on the Book of Job, Book XVI ↗

Thomas Aquinas

Lest it seem the just also are overturned together with the wicked, Eliphaz excludes this adding, "The just will see it and will rejoice," and by this he wants to say that the just will not be ruined, but will live in joy. To show that they lack justice because they rejoiced over the ruin of others he says, "and the innocent will mock them," as if to say: The innocent can mock them safeguarding their innocence by the fact that they are undermined against their opinion. In this they rejoice in divine justice. …

Commentary on Job ↗