"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. Dear friends, since God so loved us, we also ought to love one another. No one has ever seen God; but if we love one another, God lives in us and his love is made complete in us."
1 John 4:11–19 is the backbone of John's letter. The primary way Christians are to be recognized is by love. This is not merely what we feel, but what we do for others. True, godly love is the most powerful evidence of being ''born again'' as a child of God. This love comes from God, who loved us before we loved Him. When we live in obedience to God, according to love, we can be confident in our relationship with Him, and have no need to fear His judgment.
Starting a new thought in verse 11, John begins again by referring to his readers as "Beloved." The word "if" here is not used in the sense of asking a question. It's meant to be understood as "since." Since God loved us so much that He sent Jesus to die to cover the cost of our sins, we should offer a similar response by loving others. Just as Jesus offered unconditional love through His sacrifice, believers are to offer similar love based on God's example rather than our feelings or the actions of others.
It should also be noted that unconditional love does not mean accepting unconditional mistreatment. Turning the other cheek in the face of insults shows love (Matthew 5:39), but we are not called to be careless with our lives (Luke 22:36). For example, God does not desire a person to remain in a physically abusive situation in order to show love. God's nature includes protection as well as love (Genesis 15:1; Psalm 18:2). We can love others unconditionally, while also using wisdom in dealing with those who might take advantage of the love of believers (Matthew 10:16).