Dear friends, let us love one another, for love comes from God. Everyone who loves has been born of God and knows God. Whoever does not love does not know God, because God is love. This is how God showed his love among us: He sent his one and only Son into the world that we might live through him. This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins.
1 John 4:7-10
We are now beginning the central core of this letter, and this core runs from verse 7 to the end of this chapter. It is not only the central core of the letter, but it is also the central core of Christian theology. All of those comparisons at the beginning of the letter, and all of the discussion of evil, antichrists and the testing of spirits comes back to this theme, for without it, the rest of the theology of our faith is rendered meaningless. In short, what is written in this section is the one thing that gives Christianity its power and authority, and against which the gates of Hell itself cannot, and will not stand.
The last sentence in this text is the key: God loved us. In fact, he loved us while we were lost, and not loving Him at all. Yet God loved us anyway− He loved us so much that He sent Jesus to die for us. Yes, you’re right, this has already been pointed out in this letter, but here it is again, as the core of everything else: that is how important it is that we grasp this simple concept.
How could God love us so much and in spite of everything? Because God is love.
That being the case, we are to love one another, just as God loved us. Nobody can do this unless God is in that person, which is to say that person is in Christ. Loving one another as God loved us runs counter to every teaching of this world, as it also runs against our natural human inclinations. Therefore, if a person does not love, it is because God is not in him or her.