2:1 sin not. Lest anyone regard the promises of I John 1:7,9, as a license to sin, John stresses that these very promises should keep them from a life style of sin! That is, the sacrificial love of their Savior, providing full forgiveness and free salvation, should by all rights lead them to hate sin and constrain them to a life of holiness.
2:1 if any man sin. This refers to a specific sin. This provision is not applicable to a life of habitual sin. The latter would indicate that the sinner has not yet truly been born again (see note on I John 3:6).
2:1 advocate. “Advocate” is the Greek paraclete, meaning “one called alongside.” It is translated “Comforter” in John 14:16.