Expositor's Bible Commentary Commentary 1 John 1:7

"but if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus his Son cleanseth us from all sin." — 1 John 1:7 (ASV)

The positive test of knowing God is to live (lit., “walk”; GK 4344) in the light as he himself is in the light. John thus reiterates the fact that light is God’s sphere. It is his nature, and he wills that it should become ours. One consequence of obeying the command to walk in the light is having fellowship with one another. The author is combating the heresy that boasts of knowledge of and communion with God but neglects fellowship with other Christians. True fellowship with God comes through other people; fellowship with them is the proof of fellowship with God. A second consequence of walking in the light is that the blood of Jesus keeps on cleansing us from every defilement due to sin. The language reminds us of the sacrificial system of the OT, as well as of the interpretation of Christ’s death given us in the letter to the Hebrews. Without Christ’s ongoing cleansing, enduring fellowship would be impossible, for the guilt resulting from sin destroys fellowship. The results of that cleansing are forgiveness, restoration, and the reestablishment of love. John’s use of the singular “sin” reminds us that the emphasis is not on specific sinful acts but on the work of God in Christ that meets and deals with the sin principle itself.