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.
That he might destroy the works of the devil - All his plans of wickedness, and his control over the hearts of people. Compare the Matthew 8:29 note; Mark 1:24 note; Hebrews 2:14 note. The argument here is, that as the Son of God came to destroy all the works of the devil, he cannot be his true follower who lives in sin.