The Centrality of Christian Love (1 John 3:11 to 1 John 4:21).
The reference to loving one's brother, deliberately added almost as an appendage in 1 John 3:10 in order to introduce the next section, now leads on to that section where love is pre-eminent. Previously any emphasis has been on God's love for His own (1 John 2:5; 1 John 2:15; 1 John 3:1) although love of fellow-Christians has not been totally ignored (1 John 2:8-11), but from now on the thought becomes central. The emphasis has been on the fact that God is pure, unalloyed light (1 John 1:5), and His love must therefore be seen as coming from within that sphere of light, but now he tells us that from the God Who is light issues forth His holy love, for He is not only light but love (1 John 4:8). God, says John, is holy love, love which is also pure, righteous and true, and so we who live in the light should love one another, for if we are His it will be part of what we are.