Galatians 5:14 - For all the law is fulfilled in one word, even in this: “You shall love your neighbor as yourself.”
Love fulfills the Law. God is love. Through love, Jesus fulfilled the Law. Jesus, God in the Flesh, fulfilled it. Because He and the Father are one (John 10:30).
In order for us to be able to even love our neighbors, we must know what love is. If we don't know God, we don't know love, or how to love. We're empty. In the the dark. However, if we know God, we know what love is. Knowing what love is, means we will know how to love others. We are full of Light.
Now the question arises; How do we get to know Love, know God?
The answer is simple. The only way to know God is through Christ.
God sent Him, His only begotten Son, to save the world from it's sin. Sin that a lost and dying world need to be convinced of. Only God's law can do that, leading to Christ. Once the law exposes, Jesus washes away that exposure, the sin. Then we live as Christ.
This brings up another question; How do we live as Christ?
The answer would be that of Jesus's other reason God sent His Son; to show us how to live. It's in His likeness. To live as Christ, would be Christ in us. All this because of one word, Love.
The point to all of this boils down to this one thing; Put God First. Without anyone first doing that, then no one can know true love, in which you can't love others, including neighbors. It's always started with God. Everything. Even the Bible. . . .
. . . . In the beginning God (Gen. 1:1)