If we say we love God but hate any of our brothers or sisters in his family, we are liars. If we don’t love someone we have seen, how can we love God? We have never even seen him.
Suppose a believer who is rich enough to have all the necessities of life sees a fellow believer who is poor and does not have even basic needs. What if the rich believer does not help the poor one? Then it is clear that God’s love is not in that person’s heart.
But whoever hates their brother or sister is in darkness. They live in darkness. They don’t know where they are going, because the darkness has made them blind.
You have not seen Christ, but still you love him. You can’t see him now, but you believe in him. You are filled with a wonderful and heavenly joy that cannot be explained.