To Florus 2.181

On the opposite side, Cain—envious and a murderer of his brother, born from the same nature but developing through a different will—is ravaged by trembling that tears his soul apart (Genesis 4:8–14, following the Greek/Old Latin description of his trembling). Thus the apostle said that sin entered this world through one man, and death through sin, and that death so passed into all human beings who sinned (Romans 5:12). This statement agrees with catholic doctrine and lends you no help.