c. 386–397 · John Chrysostom, Homilies on Second Corinthians 15.2
By this worldly sorrow then he meaneth that which is to the harm of those that sorrow. For only in respect to sins is sorrow a profitable thing; as is evident in this way. He that sorroweth for loss of wealth repaireth not that damage; he that sorroweth for one deceased raiseth not the dead to life again; he that sorroweth for a sickness, not only is not made well but even aggravates the disease: he that sorroweth for sins, he alone attains some advantage from his sorrow, for he maketh his sins wane and disappear. For since the medicine has been prepared for this thing, in this case only is it potent and displays its profitableness; and in the other cases is even injurious. ‘And yet Cain,’ saith one, ‘sorrowed because he was not accepted with God.’ It was not for this, but because he saw his brother glorious in honor; for had he grieved for this, it behoved him to emulate and rejoice with him; but, as it was, grieving, he showed that his was a worldly sorrow. But not so did David, nor Peter, nor any of the righteous. Wherefore they were accepted, when grieving either over their own sins or those of others.