1 John 4:7
7Beloved, let’s love one another, for love is of God; and everyone who loves has been born of God and knows God.
From the doctrine just defended John draws the exhortation. Wesley: it is by the Spirit that the love of God is shed abroad in our hearts. Every one that truly loves God and neighbor is born of God.
Love is not a decoration on knowledge; it is how new birth shows. The command is meant seriously: let us love. Grace that regenerates is grace that can be walked in toward the brother.
Calvin returns to the exhortation that fills the letter: mutual love, not merely loving those who love us. No one can prove himself a son of God except he loves his neighbors; true knowledge of God necessarily produces love.
Love is of God as fountain. The born-of-God know Him in a knowledge that regenerates. Separate faith from love and you attempt to take heat from the sun.