1:7 But if we walk in the light as he himself is in the light, we have fellowship with one another and the blood of Jesus his Son cleanses19 us from all sin.20
tnBDAG50s.v.ἁμαρτία 1 defines this term as “a departure fr. either human or divine standards of uprightness” (see 1 John 5:17 where ἁμαρτία [hamartia] and ἀδικία [adikia] are related). This word occurs 17 times in 1 John, of which 11 are singular and 6 are plural.
snFrom all sin. Sometimes a distinction between singular “sin” and plural “sins” has been suggested: Some would see the singular all sin of 1:7 as a reference to sinfulness before conversion and the plural sins of 1:9 as a reference to sins committed after one became a Christian. This amounts to making 1:7 refer to initial justification and 1:9 to sanctification. But the phrase all sin in 1:7 is so comprehensive that it can hardly be limited to preconversion sins, and the emphasis on “walking” in 1:7 strongly suggests that the Christian life is in view (not one’s life before conversion). In 1 John 1:8 sin appears as a condition or characteristic quality, which in 1:10 is regarded as universal. Apart from forgiveness in Christ it results in alienation from God (2:15) and spiritual death (3:14). But according to 1 John 1:7, cleansing from sin is possible by the blood (representing the sacrificial death) of Jesus.