Dear friends, let us love one another, for love comes from God. Everyone who loves has been born of God and knows God. Whoever does not love does not know God, because God is love. This is how God showed his love among us: He sent his one and only Son into the world that we might live through him. This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins. Dear friends, since God so loved us, we also ought to love one another. No one has ever seen God; but if we love one another, God lives in us and his love is made complete in us.
This is how we know that we live in him and he in us: He has given us of his Spirit. And we have seen and testify that the Father has sent his Son to be the Savior of the world. If anyone acknowledges that Jesus is the Son of God, God lives in them and they in God. And so we know and rely on the love God has for us.
God is love. Whoever lives in love lives in God, and God in them. This is how love is made complete among us so that we will have confidence on the day of judgment: In this world we are like Jesus. There is no fear in love. But perfect love drives out fear, because fear has to do with punishment. The one who fears is not made perfect in love.
We love because he first loved us. Whoever claims to love God yet hates a brother or sister is a liar. For whoever does not love their brother and sister, whom they have seen, cannot love God, whom they have not seen. And he has given us this command: Anyone who loves God must also love their brother and sister. (1 John 4:7-21)
God is love. The supreme revelation, characteristic of the Christian faith. Other religions know of a God who is good and compassionate: no other religion has known that the dynamism of love moves the entire creation and that its source lies in God-Love.
In this beautiful text, John insists on the inseparability of love of God and love of our neighbor. We all know this, but sometimes we might wonder why it is so. John gives us the paramount reason; love comes from God. If we can love God, it is because God loved us first. If we love each other it is because God's love extends among us.
John also links love of God and faith in God: a true Christian believer is somebody who begins by "believing in God's love, and that God is love."