1 John 1:5 to 1 John 2:2. Fellowship with God Requires a Right View of Sin.
1 John 1:5-10. Spiritual fellowship depends on moral affinity. Hence since Jesus has declared the holy perfection of God, we cannot truthfully claim fellowship with Him, and at the same time be habitually committing sin. Only as we Christians constantly aim to be like God have we fellowship with Him and with one another, our sinfulness being cleansed by the blood of Christ. To deny that we are sinful or that we have committed sin proves self-deception, ignorance of moral facts, and of God's message to us in the Gospel. Our duty is to confess our sins to God and thereby secure from Him forgiveness and cleansing. Thus does John deal with the view which regarded sin as immaterial or unreal.
1 John 1:5. God is light: this is one of John's great definitions of God (1 John 4:16). Light, as here contrasted with darkness, means not intellectual illumination (for which cf. John 8:12) but ethical perfection. It describes the absolute purity and holiness of God, as He has been revealed by Christ (p. 745).
1 John 1:6. walk: a familiar Scriptural figure to describe a regular course of life. do not the truth: i.e. do not live in harmony with its demands. The life as well as the statement of the lips is false.
1 John 1:7. we have fellowship one with another: i.e. possibly, with God, but probably with brother Christians, fellowship with God being implied and the truth declared that the nearer we are to God, the closer is our fellowship with each other. cleanseth from all sin: the ritual cleansing required by the Law as a condition of approach to God has its parallel in the cleansing of the heart effected by the blood of Christ as the preface and accompaniment of fellowship with God.
1 John 1:8. the truth is not in us: i.e. we are blind to our real condition.
1 John 1:10. we have not sinned: i.e. since conversion. In any case this phrase points to acts of sin, whilst that in 1 John 1:8 regards sin as a condition or state. God is made a liar because His entire scheme of redemption assumes the universality of sin, and the same view is set forth in His Word.