We know that we have passed from death unto life, because we love the brethren.
Love is from God. God is love. That’s His nature. He can’t help but love. And His Spirit is in each of His children. We can now love unconditionally, just as God loves. That means we can love without expecting anything in return even when the object of our love is actually unlovable, in a natural way. That’s something that is hard to understand but it’s part of the fruit of the Spirit that will be seen in a person who becomes a Christian. Love covers up, or rather replaces, the hate that used to be there. Love is from God.