Augustine of Hippo

"For he has wrought deceitfully in His sight" [Psalm 36:2]. In whose sight? In His, whose fear was not before the eyes of him that did work deceitfully. "To find out his iniquity, and hate it." He wrought so as not to find it. For there are men who as it were endeavour to seek out their iniquity, and fear to find it; because if they should find it, it is said to them, Depart from it: this you did before you knew; you did iniquity being in ignorance; God gives pardon: now you have discovered it, forsake it, that to your ignorance …

Exposition on Psalm 36 ↗

Ambrose of Milan

For it is written: There is no fear of God before his eyes: because he hath dealt deceitfully before him, that he might find his iniquity unto hatred. For what did he find? For every one that asketh, receiveth: and he that seeketh, findeth: and to him that knocketh, it shall be opened. But as commendable is he who finds the good he seeks, so elusive is he who labored to find the evil he sought; for our efforts should be directed towards good things, not towards wickedness and crime. …

Commentaries on the Twelve Davidic Psalms ↗

Thomas Aquinas

But the cause is, "because he has acted deceitfully." When someone in the sight of a king does something hateful to the king, it is a sign that he does not fear him; so the sinner, when he commits sin in the presence of God, who sees all things, it is a sign that he does not fear God, because "in his sight," namely of God, "he has acted deceitfully," that is, he has committed deceit: Heb. 4: "All things are naked and open to his eyes." And he says "deceitfully," because he shows one thing outwardly and pretends another: Ps. …

Exposition on the Psalms of David ↗