1 John 3:15

Tertullian On Idolatry

even in a word of curse or of reproach, and in every impulse of anger, and in the neglect of charity toward a brother just as John teaches,[8]

Cyprian Treatise IV On the Lord's Prayer

with the Lord in the day of judgment; but the quarrelsome and disunited, and he who has not peace with his brethren, in accordance with what the blessed apostle and the Holy Scripture testifies, even if he have been slain for the name of Christ, shall not be able to escape the crime of fraternal dissension, because, as it is written, "He who hateth his brother is a murderer "[66]

Cyprian Treatise X On Jealousy and Envy

e 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 hateth his brother is a murderer; and ye know that no murderer hath life abiding in him."[24]