How is the commandment to love our brothers and sisters an old one? Well, Moses taught us to love our neighbors as ourselves way back at the time of the Exodus from Egypt (see Leviticus 19:18). John’s Jewish readers would thus have learned this commandment from childhood, and they doubtless would have tried very hard to keep it, with varying degrees of success.

But when Jesus gave the same commandment to Christians, John says it somehow became new. Why is that? Because along with a relationship with Jesus comes the ability to keep the law. When we trust Him as Savior and bow the knee to Him as Lord, His Holy Spirit comes to live within us, shining His light into our hearts. This of course gives us a greater desire to do what He tells us, because we see Jesus and His love for us so much more clearly.

But this light also helps us see other people in a different way, not as obstacles to our own will, but as fellow sinners in need of salvation. When we walk in the light, when we acknowledge the truth of our own sin, we are much more likely to be patient with other people instead of hating them, even when they inconvenience us and even when they hurt us. Living in the presence of Christ’s power and love and acknowledging the reality of our own sin makes it possible for us truly to love even our enemies.

What’s the alternative? To go on living in the darkness, blind to the reality of Christ and the needs of the world around us. Who wants to live like that?

I John 2:1-14 (ESV)

My little children, I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous.
2 He is the propitiation for our sins, and not for ours only but also for the sins of the whole world.
3 And by this we know that we have come to know him, if we keep his commandments.
4 Whoever says “I know him” but does not keep his commandments is a liar, and the truth is not in him,
5 but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him:
6 whoever says he abides in him ought to walk in the same way in which he walked.
7 Beloved, I am writing you no new commandment, but an old commandment that you had from the beginning. The old commandment is the word that you have heard.
8 At the same time, it is a new commandment that I am writing to you, which is true in him and in you, because the darkness is passing away and the true light is already shining.
9 Whoever says he is in the light and hates his brother is still in darkness.
10 Whoever loves his brother abides in the light, and in him there is no cause for stumbling.
11 But whoever hates his brother is in the darkness and walks in the darkness, and does not know where he is going, because the darkness has blinded his eyes.
12 I am writing to you, little children, because your sins are forgiven for his name’s sake.
13 I am writing to you, fathers, because you know him who is from the beginning. I am writing to you, young men, because you have overcome the evil one. I write to you, children, because you know the Father.
14 I write to you, fathers, because you know him who is from the beginning. I write to you, young men, because you are strong, and the word of God abides in you, and you have overcome the evil one.