But the one who hates his fellow Christian ¹  is in the darkness, walks in the darkness, and does not know where he is going, because the darkness has blinded his eyes. ² 

The one who says he is in the light but still hates ¹  his fellow Christian ²  is still in the darkness.

Now ¹  this is the gospel ²  message ³  we have heard from him ⁴  and announce to you: God is light, and in him there is no darkness at all. ⁵ 

On the other hand, I am writing a new commandment to you which is true in him ¹  and in you, because ²  the darkness is passing away and the true light is already shining. ³