“This is the message we have heard from him and proclaim to you, that God is light, and in him is no darkness at all.” (1 John 1:5 ESV)
“In describing God as light, John is referring to His absolute moral purity and omniscience. In other words, there is no moral defect, nor is there a lack of knowledge in God. John’s point seems to be that the person and work of Christ, which is what is announced in the gospel message, is the light that brings us into fellowship with God, who is the light.
“John’s description of God as light in whom there is no darkness at all undergirds the fact of His utter otherness and therefore His inaccessibility to fallen creatures who exist in darkness. The critical link for fellowship between creatures of darkness and a Creator who exists in absolute light is the incarnate Son of God. Without Christ, we remain in a state of darkness and alienation from the life of God.
“It is evident from 1 John 1:6–7 that John’s emphasis on the fact that God is light in whom there is no darkness at all is more than a theological abstraction. On the contrary, his concern is practical and pastoral — he admonishes his readers to ‘walk in the light as he is in the light.’ For John, embracing the gospel message brings us into fellowship with God the Father through and with Jesus Christ and with each other (1 John 1:3). The genuine nature of this fellowship is seen in a walk that reflects and responds to the truth that is revealed in Christ. Once again, we can see a correlation to Paul’s letter to the Ephesians. These calls to walk in the light of the knowledge of Christ are not offered as a means of gaining fellowship with God; rather, it is because of the fellowship that we possess by faith in Christ that Paul exhorts his readers — and us — to walk in the light. Psalm 36:9 says, “For with you is the fountain of life; in your light do we see light.” Both John and Paul make the point of full purity and knowledge in God revealed in Christ, received by believers and reflected in their thoughts and walk.
“God is indeed light, and in Him there is no darkness at all. By virtue of our fallen condition we are in a state of darkness and are thereby alienated from the life of God. But in Christ we are reconciled to God and are in fellowship with the light. The admonition is that we would reflect that light to the glory of the triune God.” ~ Ken Jones