He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
He that committeth sin is of the devil - in contrast to "he that doeth righteousness" (1 John 3:7). He is a son of the devil (1 John 3:10; John 8:44). John does not say, 'born of the devil,' as he does "born of God;" for 'the devil neither creates nor begets; but whoever imitates the devil becomes his child by imitation, not by proper birth' (Augustine, 'Tract.,' 4: 10). From the devil there is not generation, but corruption (Bengel).
Sinneth from the beginning - from the time that sin began; that he became what he is, the Devil. He kept his first estate only a short time after his creation (Bengel). Since the fall of man (at the beginning of our world) the devil is (ever) sinning (he has sinned from the beginning, is the cause of all sins, and still goes on sinning). As author of sin, and prince of this world, he has never ceased go seduce man to sin (Luecke).
Destroy, х lusee (G3089)] - break up and do away with: bruising and crushing the serpent's head.
Works of the devil - sin, and its awful consequences. Christians cannot do that which Christ came to destroy.