1 John 2:7-11. (NIV)
7Dear friends, I am not writing you a new command but an old one, which you have had since the beginning. This old command is the message you have heard. 8Yet I am writing you a new command; its truth is seen in him and you, because the darkness is passing and the true light is already shining.
9Anyone who claims to be in the light but hates his brother is still in the darkness. 10Whoever loves his brother lives in the light, and there is nothing in him to make him stumble. 11But whoever hates his brother is in the darkness and walks around in the darkness; he does not know where he is going, because the darkness has blinded him.
Living in light means loving my fellow Christians, for who is my brother here if not those who belong to the body of Christ? The truth is seen in us when we love one another, just as Jesus had earlier said (John 13:35).
Remember that John is writing this to the church. If I hate other Christians, even the young earthers, or the loudmouths on the internet who think that everybody except them is a heretic, then I’m stumbling around in the darkness myself. If I love them I will remain in the light so I’ll be able to see where I’m going and not stumble.
John writes that the true light is already here: the darkness is passing (v. 8). Soon there will be no darkness at all, only the light of God’s truth. What will the people still walking in darkness do when the darkness has passed away? Those people are my brothers and my sisters! If I am in the light, then I must also love those who are still walking in darkness. And I should not be surprised if they can’t see that I love them. How can they see when the darkness has blinded them?