Andreas of Caesarea : It may be true that the righteous person does not sin, but no one is a child of God by nature. This is why we avoid sin, not by the way in which we were made, which would make sin impossible for us, but by watching out that we do not fall into it. — CATENA Bede : We know that everyone who is born of God does not sin. Sin, namely unto death. This can be understood about all mortal crimes, and specifically that which violates brotherhood, as we have explained above. But also, the sin unto death can be said to be rightly understood as the sin prolonged up to the time of death, which everyone born of God does not commit. After all, King David committed a mortal crime. For who does not know that adultery and murder deserve eternal death? But yet David, because he was born of God, because he belonged to the society of the children of God, he did not sin unto death, because he immediately obtained forgiveness for his guilt by repenting. — Commentary on the Catholic Epistles Bede : But the generation of God preserves him, etc. The grace of Christ, by which the faithful are reborn, preserves those who are called holy according to the purpose, so that they do not commit sin leading to death; and if they err in anything due to the frailty of human condition, it protects them from being touched by the malignant enemy. Furthermore, it must be said, we remain in the generation of God as long as we do not sin; indeed, those who persevere in the generation of God cannot sin, nor be touched by the malignant. For what communion has light with darkness, Christ with Belial (II Cor. VI)? Just as (he says) day and night cannot be mixed, so righteousness and iniquity, sin and good works, Christ and Antichrist, the malignant one and the generation of God. — Commentary on the Catholic Epistles Bede : We know that we are born of God, etc. We are of God, regenerated by His grace and baptism through faith, and saved so that we may endure in faith. However, the lovers of the world are subjected to the enemy, either never freed from his dominion by the wave of regeneration, or after the grace of regeneration, returned again to his dominion by sinning. Not only the lovers of the world but also those who are recently born and do not yet have discernment of good and evil, because of the guilt of the first violation, belong to the kingdom of the evil enemy unless by the grace of the kind Creator they are rescued from the power of darkness and transferred into the kingdom of the Son of His love (Colossians 1). Hence, he did not simply say that the world is in the evil one but added, And (he says) the whole world is placed in the evil one. For as blessed Ambrose says: "We are all born under sin, whose very birth is in defect." And Pelagius strives in vain to affirm that infants recently born have no need of the grace of baptism to be reborn, because they are said to be born as clean from all stain of sin as Adam was created in paradise, deriving no stain of original guilt from him, and being guilty of nothing until they begin to sin by their own will. But as for us, setting aside the poisons of the Antichrists, which are condemned and expelled from the Church all through this Epistle by the one who drank from the breast of the Lord, the fountain of life, let us hear in the closure the good word of salvation which he pours out for us. Let us observe the works of the supreme King which he tells of. The following ensues: — Commentary on the Catholic Epistles Didymus the Blind : If it is true that when someone does what is righteous his power to do so comes from God, and if it is also true that righteousness and evil cannot live together, then it is perfectly clear that as long as a person does such things he is righteous and does not sin. But because this ability is given by grace and is not natural, John adds that the righteous person must watch out, so that evil will not touch him. — COMMENTARY ON 1 JOHN Oecumenius : We know that whoever is born of God does not sin, but he who has been born of God guards (τηρεῖ) himself, and the wicked one does not touch him. Having declared this, he subsequently indicates whose sin is the sin leads to death; and he says that whoever is born of God does not sin. For when he has once entrusted himself to the one dwelling in him through adoption in Christ, he remains inaccessible to sin. However, lest anyone think that such a nature has been completely changed, so that he can no longer be seized by sin, he adds: "He guards himself," as if to say: Unless he were to keep and guard himself from the evil one, he would certainly sin. Therefore, it is not nature that leads to perfection, but rather the glory of God, who, because He has adopted us, has deemed us worthy of such grace: that by keeping and guarding what has been given to us by Him, we may also have it, so that we do not sin. — Commentary on 1 John Tertullian : Chapter V.-Sin Never to Be Returned to After Repentance. — On Repentance