1 John 4:13-21 (ESV)
"By this we know that we abide in him and he in us, because 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.  Whoever confesses that Jesus is the Son of God, God abides in him, and he in God.  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.  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.  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.  We love because he first loved us.  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.  And this commandment we have from him: whoever loves God must also love his brother."
“By this we know that we abide in him and he in us, because 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.” So often I have seen this used by different people to speak of their own faith, election etc. At which point the Holy Spirit is confused with emotions. “I know I abide in Him because I had this totally awesome experience at this Christian rock concert….” But this isn’t meant to be an indicator of how we as Christians today know that we have abide in God, and him in us. But rather how John and the disciples know. They were given the Holy Spirit in very tangible knowable ways, after having been promised the Spirit by the Risen Lord Jesus. This is meant for our edification in a secondary way, that we can be certain of what John says, because he was given the Holy Spirit.
We can know that God abides in us, because we confess that Jesus is the Son of God. That is because of our faith in God. This faith in God, though, moves us to love. So we are back on that. We cannot hate our brother and love God. (One might have to recommend that with "If anyone comes to me and does not hate his own father and mother and wife and children and brothers and sisters, yes, and even his own life, he cannot be my disciple.”( Luke 14:26 (ESV) Yet this is not hard to do.) If we love God, we will love our brother also. We will not let our brother stand between us and God, and by this too we show love for our brother, but we will love our brother. One cannot hate his brother and love God. The love of God, moves us to love our brother. In fact it is just there that we love God, by loving our brother who was created in the image of God, and redeemed by the blood of God, Jesus Christ, with which same blood we to were redeemed. The highest order of love then is to love our neighbor as God loves us, and though this has to do with following the Ten Commandments as was stressed yesterday, so it also has to do with forgiving. God Loves us by forgiving us. So we love our neighbor forgiving them as God has forgiven us. We cannot live, nor can we love, without forgiveness.