This then is the promise which we have heard of him and announce unto you, that God is light, and darkness is not at all in Him.1 John 1:5
John now commences with the body of his joyful message. The word order in Greek is unique and masterfully emphasizes that this message is, i.e. exists.1 Then he moves on to the content of the announcement. He begins with the first of many contrasts.
This letter contains a series of contrasts: light and dark, truth and lies, love and hate, Christ and Anti-Christ, life and death, born of God and born of the devil, etc. If this epistle were a photo, it would be notable for its high contrast. The darks would be pitch black. The whites would be shining bright.
The first contrast which John introduces is that of light and dark. The apostles received a promise from the Eternal Life which came in the flesh. They heard this promise from Jesus––who is the manifested Life––and now announce it to the world.
God is light, and in Him is no darkness at all. Or as I have rendered it to draw out the double negative found in the Greek: ”darkness is not at all in Him.” John is at pains to make plain that God is not a yin-yang. Darkness (I.e. sin, evil) can have no fellowship with God. Christ coming in the flesh is the basis for our fellowship with God (1:3), but God is light, which means that our moral darkness will need to be dealt with.
This raises a problem which John will soon answer: how can sin-darkened man can dwell in God? The starting point to answer that question is this statement of God’s being. He is light. Note too that John is providing foundational language which will moor the church throughout the ages. God is light (1:5). God is love (4:8b). Christ is the eternal life of God manifested in the flesh (1:2). Make no mistake God’s nature and character are foundational for true religion, for true fellowship with God.
1 Kistemaker, James, Epistles of John, Peter, and Jude. Pg. 241