Jesus articulated what is known as the Golden Rule in Matthew 7:12: "So whatever you wish that others would do to you, do also to them." The Golden Rule exemplifies Jesus' teachings on love and righteousness, reflecting God's character and guiding believers towards living out their faith in practical, transformative ways. While the Golden Rule provides a good principle for all to follow, only those whose hearts are transformed by God following salvation can truly live out the Golden Rule. While other religions teach a reciprocal rule in treating others, discouraging others from doing things they would not want done to them, the Golden Rule calls for genuine love and care that comes in proactive and positive action toward all.
Do we naturally seek to do good to our fellow men, entirely unselfishly? We do not. The wonder of God's work in the heart is that He puts His own love for humanity in our hearts for one another. John reminds us that "No one has ever seen God; if we love one another, God abides in us and his love is perfected in us" (1 John 4:12). What this means is that when we love each other, we glorify God and His image can be seen in our love, which is ultimately His love.
This command to love makes Christianity unique when compared to every other religious system. In fact, the Bible is so radical in its command to proactively love that Christians are told to love even their enemies, something that simply does not exist in any other world religion (Matthew 5:43–44; cf. Exodus 23:4–5).
The mark of a true Christian is this kind of unselfish love (John 13:34–35). God's Spirit of love is alive in the person who loves in this unselfish, supernatural way—and the presence of that Spirit is evidence of a Christian's salvation. First John 3:16–18 makes it clear: "By this we know love, that he laid down his life for us, and we ought to lay down our lives for the brothers. But if anyone has the world's goods and sees his brother in need, yet closes his heart against him, how does God's love abide in him? Little children, let us not love in word or talk but in deed and in truth."