Love has to run through every part of the Christian life (v11).  John has previously spoken of the necessity of love in the context of light and darkness (2 v7-11). This teaching is based on Jesus’ words in the Upper Room (John 13 v34-35) and Old Testament passages (Deuteronomy 6 v5; Leviticus 19 v18).

Cain is used as an example of hatred (v12-15). He killed his brother because his heart was jealous of his righteous brother (v12). Hatred is a mark of a world that hates Christ and righteousness (v13) and a mark of remaining in spiritual death; love is the mark of having passed into eternal life (v14-15).

Jesus is given as an example of love (v16-18). The reason love must be such a vital part of the Christian life is that love is such a part of Christ’s life. Jesus’ sacrificial death is particularly the supreme example of love (v16). True love has to be truly sacrificial (v16b). We can’t lightly pass over this statement.

The love that is called for is a love a genuine compassion and action (v17-18). This is a love based on the truth of Jesus, it flows from faith. Paul teaches that the only thing that counts is ‘faith working through love.’ (Galatians 5 v6).

Not having this love is a denial of the faith (v17). A lack of love shows separation from the God of love.