And every man that has this hope in him purifies himself, even as he is pure.
All Commentaries on 1 John 3:3 Go To 1 John 3
Tertullian of Carthage
AD 220
Accordingly he says more manifestly: "And every (man) who has this hope in Him makets himself chaste, just as Himself withal is chaste.".
And accordingly, "he who is being born of God does not sin, because the seed of God abides in him; and he cannot sin, because he has been born of God. Herein are manifest the sons of God and the sons of the devil."