11 Why do you rush into the darkness of jealousy? Why do you enfold yourself in the cloud of malice? Why do you quench all the light of peace and charity in the blindness of envy? Why do you return to the devil, whom you had renounced? Why do you stand like Cain? For that he who is jealous of his brother, and has him in hatred, is bound by the guilt of homicide, the Apostle John declares in his epistle, saying, “Whosoever hates his brother is a murderer; and you know that no murderer has life abiding in him.” And again: “He that says he is in the light, and hates his brother, is in darkness even until now, and walks in darkness, and knows not whither he goes, because that darkness has blinded his eyes.” Whosoever hates, says he, his brother, walks in darkness, and knows not whither he goes.
For he goes unconsciously to Gehenna, in ignorance and blindness; he is hurrying into punishment, departing, that is, from the light of Christ, who warns and says, “I am the light of the world. He that follows me shall not walk in darkness, but shall have the light of life.” But he follows Christ who stands in His precepts, who walks in the way of His teaching, who follows His footsteps and His ways, who imitates that which Christ both did and taught; in accordance with what Peter also exhorts and warns, saying, “Christ suffered for us, leaving you an example that you should follow His steps.”
Source: The Treatises of Cyprian (New Advent)