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.

 John is not setting before us a terrifying perfectionism; but he is demanding a life which is ever on the watch against sin, a life in which sin is not the normal accepted way but the abnormal moment of defeat. John is not saying that the man who abides in God cannot sin; but he is saying that the man who abides in God cannot continue to be a deliberate sinner. 