Augustine of Hippo

"Keep innocency" (ver. 37); keep it even as thou usedst to keep thy purse, when thou wert covetous; even as thou usedst to hold fast that purse, that it might not be snatched from thy grasp by the thief, even so "keep innocency," lest that be snatched from thy grasp by the devil. Be that thy sure inheritance, of which the rich and the poor may both be sure. "Keep innocency." What doth it profit thee to gain gold, and to lose innocence? …

Exposition on Psalm 37 ↗

Ambrose of Milan

Keep innocence, and see equity. Whoever keeps innocence, sees equity; for whoever is pure sees God, whose staff is upright, and upright is his justice; to turn away from those who turn to the pursuit of wickedness. Blessed is innocence, which sees God. Finally, others have added: Keep perfection; for he is perfect who knows no evil, nor does he know deceit. Therefore, it says: Keep perfection; for there are remnants for a peaceful man. Relics are said to be from the body of the dead, from his remains. …

Commentaries on the Twelve Davidic Psalms ↗

Thomas Aquinas

"Guard innocence, and see equity." Here he exhorts to the justice that is toward one's neighbor; and regarding this he does three things. First, he sets forth the exhortation; second, the reward, at "For there are"; third, he expounds what he said, at "Salvation." A person should do two things for his neighbor: first, not harm him; second, render what is due. Regarding the first he says, "Guard innocence," harming no one. …

Exposition on the Psalms of David ↗