Gregory the Dialogist

He will look on men, and will say, I have sinned. He would not know himself to be a sinner, if he had not righteousness. For no one detects his own deformity, except when he has begun to be upright. For he who is altogether deformed, cannot perceive what he really is. But he who is conscious that he is a sinner, has begun in some measure to be righteous; and from being righteous, blames his conduct when yet unrighteous. …

Morals on the Book of Job, Book XXIV ↗

Thomas Aquinas

But this is not possible unless man humbly recognizes and confesses his sin, and so he says, "He will consider man," as if spontaneously offering himself for the confession of sin, and so he continues, "and he will say, 'I have sinned.'" So one does not think that he has said this from humility he adds, "and I have truly perverted what is right." He says this against Job because Job had said, "I have not sinned and my eye lingers on bitter things." (17:2) In his confession he will not lament about the gravity of the punishment, and …

Commentary on Job ↗