He who sins is of the devil, for the devil has been sinning from the beginning. To this end the Son of God was revealed, that he might destroy the works of the devil.
8 He that committeth sin, This word, to commit, or to do, refers also to outward works, so that the meaning is, that there is no life of God and of Christ, where men act perversely and wickedly, but that such are, on the contrary, the slaves of the devil; and by this way of speaking he sets forth more fully how unlike they are to Christ.
The apostle, having alleged the believer's obligation to purity from his hope of heaven, and of communion with Christ in glory at the day of his appearance, now proceeds to fill his own mouth and the believer's mind with multiplied arguments against sin, and all communion with the impure unfruitful works of darkness. And so he reasons and argues, I.
Commenting on 1 John 3:4-10
That is, "So far as a man sinneth, so far he is of the devil, and like unto him, in whom sin is predominant: he having been an old sinner, soon after the beginning of the creation, and a bold tempter to sin all his days." Learn, 1.