1 John 4:7-21 teaches that God is love by nature, and everyone who truly loves others is born of God and knows Him, while those who do not love do not know God. God's love was revealed through sending His Son as an atoning sacrifice for our sins—not because we loved Him first, but because He loved us first. Therefore, believers must love one another, as this perfect love casts out fear, perfects us, and proves our abiding in God; anyone who claims to love God yet hates their brother is a liar, for loving the visible brother is essential to loving the unseen God.