If we say that we have fellowship with him and walk in the darkness, we lie, and don't tell the truth.

 1:6-7 If we say that we have fellowship with him and at the same time walk in darkness, we lie and are not doing the truth. But if we walk in the light, as he is in the light, we have fellowship with each other and the blood of Jesus Christ is steadily cleansing us from all sin. 