Invisible Love Made Visible – The Letters of John
The world will know (can be assured) that God exists and that He loves them when they see believers loving each other.
1 John 4:7-21
God Is Love
7 Beloved, let us love one another, for love is from God, and whoever loves has been born of God and knows God. 8 Anyone who does not love does not know God, because God is love. 9 In this the love of God was made manifest among us, that God sent his only Son into the world, so that we might live through him. 10 In this is love, not that we have loved God but that he loved us and sent his Son to be the propitiation for our sins. 11 Beloved, if God so loved us, we also ought to love one another. 12 No one has ever seen God; if we love one another, God abides in us and his love is perfected in us.
13 By this we know that we abide in him and he in us, because he has given us of his Spirit. 14 And we have seen and testify that the Father has sent his Son to be the Savior of the world. 15 Whoever confesses that Jesus is the Son of God, God abides in him, and he in God. 16 So we have come to know and to believe the love that God has for us. God is love, and whoever abides in love abides in God, and God abides in him. 17 By this is love perfected with us, so that we may have confidence for the day of judgment, because as he is so also are we in this world. 18 There is no fear in love, but perfect love casts out fear. For fear has to do with punishment, and whoever fears has not been perfected in love. 19 We love because he first loved us. 20 If anyone says, “I love God,” and hates his brother, he is a liar; for he who does not love his brother whom he has seen cannot  love God whom he has not seen. 21 And this commandment we have from him: whoever loves God must also love his brother. (ESV)
 4:20 Some manuscripts how can he